Man, that is alot of firsts on one bow! The only thing I would say is to get the lower limb to try to match the upper limb if you could. Since it is sinewed, it would not hurt as much or take as much set if you tillered it a bit to match the upper limb. That will get that upper spot that is bending alot that everyone has pointed out to calm down a bit. Just removing a little bit of material on the bottom limb, then shooting it in a bit, and then tiller check. Over time that spot could give you alot of set especially if the bottom limb is a good deal stronger. Osage is a tough wood in compression and a dramatic bend in osage will not be
"as" bad as in other woods would though, and osage can take it alot better than most any other wood could. I bet it shoots great though! I really like the braced profile of your bow. The snake skin looks great. I haven't skinned a bow ever. And if it shoots good now, just give that bow a good year of seasoning, and it'll have at least a bit more reflex/less set than is has now, and be pulling 55# - 60# @ 28", and it'll be spitting fire. Nice bow! You got me inspired steve, I need to go start breaking out the sinew myself...
EDIT: Having a tiller tree that you can step back and look at makes tillering so much easier. I use basically a giant version of the simple tiller tree's people use though. Although it doesn't have a pulley, it doe's make things alot easier, maybe just because it is sturdy and at eye level.