At 240#, wanting a boat good for camping and multiple day outings, you would probably approach listed max capacity of 315 lbs on the Stratos. But look at the design, and the side view of the hull. https://www.dagger.com/us/kayaks/stratos-145-l Convex curves from the keel to the deckline, and rocker from end to end along the keel, add up to how they describe the hull - designed to excel in surf and rock gardens. This allows for a lot of maneuverability.
The Tsunami 145 lists a max capacity of 350 lbs. It’s listed an inch wider, and probably also deeper, which allows for more capacity. That gives you a little reserve. If you’re actually approaching manufacturer’s listed capacity, while it’s not a definitive thing depending upon the boat and the paddler’s abilities and preferences, it’s probably worth test paddling at that weight. So a little more reserve capacity with the Tsunami. Now look at the side view of the Tsunami. https://www.wildernesssystems.com/us/kayaks/tsunami-145 Notice less rocker, and notice the convex curve at the stern between the keel line and the deck line. This leads to better tracking, and less maneuverability.
These are advertised at 56 and 57 pounds, so weight is not really a consideration.
I know you haven’t asked for this or suggested any interest in it, but I like to point out options in the case they may prove helpful. Being 6’ around 195 lbs, I consistently note something in shorter boats that lighter people probably don’t. At my weight, shorter kayaks that are still around the same width simply sink in the water further, and pretty much cancel out the added maneuverability that a lighter person gains with a shorter boat. And they’re just a little more sluggish than they assuredly are with a lighter person. Now I don’t know how much paddling you’ve done and your skill level, and I have no idea what would constitute “a real beast” in your mind. To one person, it’s a sluggish boat trying to paddle against the current. To another person, it’s a boat that they can’t seem to get to track straight. To the next, it’s a person who’s nervous and unbalanced about maneuvering, and is having a hard time with that. But with some basic skills, I would want a guy your size to at least try something like a Current Designs Sirocco. https://www.cdkayak.com/Kayaks.aspx?id=41
Now I do sea kayak a lot, so take that into account. But for paddling those rivers, the Sirocco will be faster, sportier feeling, and maneuvers more than well enough, to add up to a lot better craft for me personally for those uses. So it would seem a shame to not try one on for size and feel in comparison, should you have the opportunity.
Where you carry your weight can make a big difference. If it’s in the thighs and butt, just make sure you’re not squeezed into a cockpit, as that’s no way to spend hours on the river. There are lots of salespeople guilty of the “It’s supposed to fit quite snugly for better control” line. And I suspect many don’t paddle enough to appreciate that snug fit would still mean a fingers width of room everywhere for your purposes.
Good luck, and enjoy whatever you end up paddling!
