512m perm gen?

[Colindapieman]

I was reading on the forums that the perm gen is 256 if you allocate over 4gb of RAM. I happen to run a modpack with 131 mods, a 128x sphax texture pack, and GLSL shaders. FTB gives an option for additional java parameters so I can give it 512m of perm gen, allowing me to run at about 30-40 fps. This is inconvenient because I have to manually add the mods to the modpacks that exist. Technic is much more refined, but lacks java parameters. Would it be difficult to add this? With 8gb of ram allocated I assume it gives 256m permgen, which gives me 20-30 fps with lag spikes every half second, making it unplayable.

Any workaround or plans to implement this?