Generaly, more mast rake does give more weather helm IF all other things stay equal....
Dont forget that by changing the rake of the mast, you are changing the sheeting angle of the mainsail. with an upright mast, the sheet is pulling down more and inducing leech tension which will be a factor in giving weather helm. By raking the rig, the sheet is flattening the sail more and letting the leech open up = less weather helm.
It is always a problem in boomless cats that as you hit a gust, you become overpowered and sheet off, this lets the sail get fuller and more powerful and also gives weather helm. so what you need to do in a gust is sheet IN !