I suggest a similar aluminum step ladder. I carry one of these in my truck where it is really a problem, but needed it on the wife’s Honda Passport.
She will stand on the floor with the door open and do the straps. I have more body that gets in the way and after years of working tend to go for more stable work platforms.
Does the RAV4 have roof rails already? The rails are a funny shaped strip that sticks up about 1.5” and runs from front to back. What kind of kayak do you have? If it is a rec kayak being 10’ I think it is it will likely mount upside down against the cockpit opening and or deck and then you put straps over the hull and around the cross bars. There is a way to loop cam straps so that the kayak pulls down tight. It is also recommended to run one strap or line from the bow and one from the stern and attach them to the car front and back.
There are also J cradles that are handy if you need to haul two kayaks and they hold them on edge. Then there are hull cradles where the kayak sits upright.
For me the simplest is upside down on the rails if you just have one and will be loading it from the side.
Do you have problems with the 40 pound weight lifting it over your head and then sliding the kayak on from the side?
There are tricks and tips if you do and maybe even the type of rack and cradle you get will depend on your ability to how you will lift it.
Celia has a Thule Hullivator on her new RAV, a bit pricey but it would make the loading the easiest. Though 40 pounds is not terribly heavy, the fact that the boat is so short probably complicates getting it angled up on the rack, especially for a shorter person. I’m 5’ 4" and nearly always solo load my boats on a regular Thule crossbar rack on a Mazda CX5 which is only an inch shorter than a late model RAV4.
I suggest you get a standard Thule crossbar set that will fit on your RAV model and then practice loading it with that. You may find you are actually more able to do this than you may fear. I second the suggestion to carry a small lightweight step stool. But place the straps around the roofrack BEFORE you slide the boat onto the rack. Much easier than trying to reach up and around the boat once it’s up there. And get loooong straps (I used 15’ ones) so you can lay them towards the hood and tailgate and then just pick up the ends and walk or flip them over the boat to fasten under the near side of the boat under the rack.
I suggest you skip the above recommendations and contact Marshall at The River Connection for his advice on a setup starting with Yakima towers and flat rails. Reason is that the Thule mounts for the cross bars with the dratted flush rails in the current Rav4 are a PITA to just pull on and off like the Cross Country mounts were for the raised rails. I ended up leaving the cross bars on thru this last winter where I used to pull them off because of it being such a bother. Hits the gas mileage and makes automatic car washes challenging.
Yakima has mounts for this car where you can take the cross bars off and leaved the mounts in place, look quite similar to how the Yakima mounts worked years ago on our flush rails in the Sable wagon. There are Yakima bars that will work with the Hullivator if you want to take that step later on.
Marshall can tell you what this setup is. Personally, when what I have ages out I will be going that way. It’ll be worth the money for the easier seasonal switch.
The biggest problem you are going to have is that your boat is so short, it’ll be harder to get it propped to slide up. I absolutely recommend against J’s. I suggest instead starting out with a decent set of cross bars, per my above suggestion, and something like foam blocks that will be easier for you to slide the boat over. That with straps to the cross bars and a bow line will be plenty secure used correctly.
You will need a towel or a rug or something that will stay put to go over the spoiler in back, because you are going to be shoving the boat up from the ground over it. Or a bar that extends well out from the car on the side from the rear cross bar of the rack, prop the boat on that then shove it into place. A tall stool or a stepladder to stand on for the strapping. And affixing the bow line.
Celia’s recommendations are very good. Tall cars and short kayaks are a tough combination but a little experimenting should help you find a workable solution. Start with the foam blocks as they are inexpensive and handy to have, before buying a more expensive cradle system that may or may not work. Making it as easy as possible to load and unload your kayak yourself will make you more likely to use it.
I use Marco saddles (V shaped) and a bathmat. Works really well for me but my roof is a little lower (Subaru Crosstrek, my parents have a Rav4 so I have seen the height difference with the two cars side by side). My kayaks are all longer, ranging from 12.5 to 18 feet. The 12.5 is by far the most awkward to load.
What is most important for longer trips is how well your boat is affixed to the cross bars and at least a bow line. So if something does start coming loose you will see it in front of you before the boat becomes a flying object.
Having a third party additional thing like stackers can be argued to help, but even with that the strapping to the cross bar is the most important. I do longer trips with two straps at each point over the boat, that way if one fails the boat is still not going anywhere. I do that both for the saddle and glide pads I have on one side AND each Hullivator cradle on the other side. My boats don’t move.
I have used various devices, but for a basic 10 footer the foam blocks and a good job of strapping including double straps with a bow line is fine. If you stop somewhere just tug on the straps, make sure they are still tight.
The biggest issue you are going to have is sliding a somewhat short boat over to the top of a very tall car. The reason I suggest the foam blocks is that it gives you the easiest ability to get it basically up there then adjust the position. All you have to do is get it anywhere over the bars then you can get on a stepladder and better position it. Trust me, with how tall these cars are now and the big spoiler you don’t want to have to aim any more than necessary up there.