I researched the subject quite a bit a few years back. Spoke to some that had done it. Watched my friend bend my straight grip 28g Repro. It moved about 1/4" down, but seemed to come back about 1/8" later. I Built my jig. Bent 3 stocks successfully. The first one was a early 1900s Parker that we (me and the owner of the gun) bent together. We moved that stock up 3/4" in 2 steps. The second was my 28g Repro which I bent down about 3/8" or more.
In the few that I've done, I believe it's very important to have a favorable grain alignment. After that, I think a paraphrase of Elmer Keith's saying is in order: "Use enough heat".
Forcing the wood will result in either breaking, cracking, or the stock returning to the original position. My repro bent easily by finger pressure after it was heated well and through. It was then held in place by the jig (not forced to bend by the jackscrews of the jig) and allowed to heat further to stress relieve the wood. It hasn't come back any in the years since I bent it.
I'm not an expert, but I didn't think this was rocket science. Larger pieces of wood are bent much much more in all kinds of things than the little we need our stock bent. Adequate heat is all I see is needed.
The Repro
Threaded Mode