I’ve used a couple heavy, steel, cheaper models - but this has been a terrific product for truck bed extension and as an effective incline (using intermediate positions) for car-top loading too. Mine has had a lot of use for more than five years. Holds up very well. Excellent quality.
Edited to add: You’re welcome. The variable lengths are helpful. Different extension settings allow car topping (with a Chevy Colorado) an eleven foot canoe, or a twelve foot canoe, a 14 foot rec kayak, or a sixteen foot sea kayak - each one secured at three points. After loading, the variable incline and height adjusts to fit under the stern. I add a strap there and red flags. It works the same way for using a truck bed.
I especially like the powder coated aluminum. The workmanship is excellent and the welds hold up better than steel (I once had a steel extender weld fail) It stood up to saltwater better than my older steel versions. Much lighter too.
If you (or any friend you have) can weld, those kind of extension carriers are very easy to make yourself.
You use square tubing and weld them to the size you need for the kayak you have. If you weld them in a way to have removable male/female sockets they can be made to take 1 or 2 kayaks. The tubing that enters the hitch receiver must be of the correct size but the rest can be made of any size squire tubing or round tubing you want to use, so making it very strong and yet light weight is easy to do.
What I recommend is to make a removable wood rack that can be lifted and tied into the bed with the top of the rack sticking up about 4" over the cab. On that rack you screw and glue 2 cradles to hold the hulls of the kayaks you want to carry. The whole thing when made from 2X4 and 1X4 braces is light weight and is simply set into the bed when you need it and tie it down.
Then make the hitch extension to come up and back as far as needed and weld a cross arm to it so it also can carry 2 kayaks. Weld a loop at each end of the cross arm for ropes to hold tension which keeps it from shifting and vibrating a lot as you go down the road. If you make the up-right and the cross arm with male/female sockets you can drill through for 3/8" bolts and assemble it very quickly and easily when needed, but when stored it takes little room because you simply un-bolt it and slide it apart. That makes it easy to store and also easy and fast to set up because you need not handle the whole thing at one time and fight it’s bulk and weight.
As a side not: make the steel crossbar a bit lower then the wood cross arm. That makes loading and unloading the kayaks very easy. If you have a 6" drop from the rear to the front the kayaks slide up easier and slid off easier and are much easier to control especially if you need to load or unload in wind.
As I said, you need the ability to weld, but if you can the only tools you need are a saw to cut the metal, a drill, Tri-Square, a wrench to fit the bolts and nuts and I also use a tap to thread the one end of the holes. If you do the same you need 2 drill bits, one for the tap size and one for the clearance size. I drill and tap the female sockets on one end for the bolts to thread into. I then run a nut down over the end of the bolts and tighten with a wrench so I have the bolt threaded into the frame itself and a nut to add security over the outside shaft of the bolt. Doing it that way is super secure and strong, and yet takes very little time or effort to assemble or disassemble it.
Look at pictures of the commercial offerings and just make one similar, but one that suits your needs exactly. By making it with male/female sockets you can make it to any size, height, length and to fit any type of kayak or canoe you need it to. With new steel (at the price of metal today) they are not super cheap to make, but not bad either. If you have access to a scrap yard and can cut your own to lengths (as per your own plan) you can get the steel for scrap-iron pricing.
Take a bit of time to clean the metal and paint it when done and it looks great and costs very little.