You can use Sydneys method with boiling water instead of oil on an unfinished stock. I've done two stock this way to put some cast off in a couple of pre-carves. This was in an old archived post I think by Allen Martin. (Although, I used a ratchet strap tied to my truck bumper instead of the clamps). As stated, you have to go farther than the amount of castoff you want because there will be some natural spring back.
Regarding your question, it would be difficult to try to get a bent forestock really straight because of the spring back effect. However, I'm sure it would help your forestock quite a bit if you just clamp it with the barrel in and sides supported, hit the bent area with some boiling water, and leave it for a couple of days with maybe a fan blowing on it to help dry. I would be worth a shot to me, and you might take quite a bit of the bend out by simply doing this.
Top Jaw