Natural reflex is desirable, as long as you have a plan, and it's not too extreme. A lot of split staves dry into reflex, too. Knots on the back are fine, but you have to work them right, and same with the belly, but it's a little easier to work them right. Remember, though, that all-important intact growth ring on the back. If you are trying to use the natural bend AND place the knots where you want, sometimes you can't have both.
So, lets say I find a great 4" dia elm sapling that only has a few knots and is "clean" despite a long slow curve to it, no twist, even curve, etc..... let's say I can get a 68" section out of it, and over that length the curve is 2.5" at the middle, if you stretch a string tip to tip. In a perfect world, I would split it into two staves, one deflexed, and one reflexed.
From the reflexed stave, I would make a reflexed flatbow or Molle and temper the belly, expecting that I'd have 1 or 2" of set with either, style, and end up with basically a setback handle and maybe just a little reflex in the limbs. I would take the deflexed stave, shorten to 64" and recurve the tips until they end up maybe 1.5-2" ahead of the handle, heat treat, and expect enough set to put the tips just level with the front.
But, knowing sapling staves, even if you split the two perfectly, since it's a sapling they will try to twist, warp, etc, and the reflexed stave will try to curl into even more reflex, etc... so pick the best one, decide what you want it to do, and make it do that while it dries on the form, and then cook it there if you have to.
