I've had it on the tiller and it barley flexes at 45#, but I can see which limb is stiffest and take some off the other one. I've been chasing growth rings on the belly a bit, really just to try and get a fairly consistent thickness of sapwood. On a stave from a fairly small diameter log it can be tricky to know how much to remove, so roughly following a ring can help avoid breaking through to heartwood.
There is one group of small knots that bulges up on the belly, I've left it proud, but I can still see a change of colour where it's more like heartwood, this is because the heart sap boundary doesn't actually correspond to a ring, it can bulge up where there are knots or it can simply wander about not concentric to the rings. "Ridgeback" is a good example of this in a longbow.
It's beginning to flex fairly evenly now, there's still a way to go before I can get it braced, but it's starting to move and I'm getting a feel for it.
One feature is a drying crack in the sapwood which isn't a problem, but will look alarming to someone who doesn't understand wooden bows, I may fill it with a wafer thin sliver of sapwood or sapwood dust and epoxy, but I have a sneaky urge to get some Walnut or Purpleheart dust to make a feature of it. Meanwhile I'll follow my mantra of when in doubt don't!
Here are a couple few pics showing some of the features, one pic shows how the drawknife is likely to tear in on a knot and that's the point to stop and use a rasp, other shows the heart/sap on the end of the limb and the drying crack. Last pic shows a knot which is a bit loose and manky, this will get picked out and filled, but it may well disappear as the belly is worked down.
Update:- Saturday morning I've been working on the left (lower) limb which was stiff, this is about the 4th time I've had it on there, and it's just starting to move at 45-50# draw weight. The outer limbs need to work more, but it's a matter of working on the knotty areas trying to get a vaguely even thickness taper and bend. Too early for any real decisions on tip shape etc, but it's getting there.