I think that either the top one will break, or the others will be overbuilt if they all are made for the same poundage.
Longer levers decrease (tighten) the bend radius of the working limb, so the limb will have to be thinner to keep the stretching and compressing of the wood fibers within allowable limits. But a thinner limb bends more easily (stores less energy), so it must be made wider to compensate.
It looks like you are going to make them all the same width. If you can get 50# out of that long-levered bow without it breaking or becoming a limp noodle, then that means your oak will handle more stress than the other two designs will place on it, since they will have greater (less tight) bend radii. Unless they are made thicker in the working limb, you won't be working the wood fibers very hard (overbuilt), and if they ARE made thicker, they will be much higher poundage than the other bow.
In other words, I think that the width of the working limb should increase significantly as you make the levers longer, if you want to get meaningful results. You could still do this with your blanks as you have them now, but you might need to drop the target draw weight some.
I would start with the longest-levered one, and see what kind of poundage it will handle without taking excessive set, then make the others to that poundage, narrowing the limbs as necessary to achieve target draw weight with minimal set.
Whatever you decide to do, I'll be looking forward to the results.
-Robert
