Hi Aikenn,
The two sets of stabilized moose I've put on to knives have done that on me during the build, but the bow was only slight and I was able to pull them back together with clamps, epoxy, and rivets. But this was on fixed blades so not sure how thin you need to get for a folder. I also epoxied a thick liner (vulcanized paper) to help hold them straight while I continued the build.
Had I continued to have trouble I would try this advice in "antler straightening" post #2. From what I've read online since I got into knives, it looks like common practice to use heat and I would hunt down more info online on how to do this. I might try to find it in relation to gunsmithing to or think of other applications where people would need to do this.
Final thought though, is that I have non stabilized moose and karboo that will not do this because they are already dense. These more dense peices that haven't warped were already dry before I cut them and have come near the crown. The crown peices that had either no visible vein (moose) or only a small vein (karboo) of pith. The ones I have that like to bend have pith showing on the inside.
Hope the little experience helps and you find what you need. Good luck on the build.