Mass principle from tbb may be better for estimating if it's being strained too much.. But the *2 rule seems great for straight bendy bows
I don't see why you can't have a 50" wood/something (sinew? grass? linen?) composite bow pull 32", it's just gonna stack and have an acute string angle unless it's some kind of crazy design. should probably be wide & made of a dense wood.
Doesn't seem like an easy task to do well though. I mean just taking a 50" hickory stick, cable backing, deflexing it and it'll probably stand 32". haha. but it probably won't perform very well..? It'd probably be a sluggish piece of trash. I should try it and see. Ugh, without recurves and no reflex, it would stack horribly...
I think it'd be a lot more practical for most people, hypothetically, to have something like a 53" bow with 28" draw. I don't see why it wouldn't work well with, say, Osage with short hooks and wide limbs? If I were to try it, I'd try to figure out a target mass from the mass principle, and try to do no set tillering.