I've tried everything I can see I can change including turning off the actual MushoomIsland Biome generation to no avail. Regardless of what genWeight I set I still get tons of MushroomIsland Biomes all over the overworld not even as islands. Has anyone else had this issue? or better know how to fix it?
I'm using the available cfg files for the RTG+Bop files as a base. I've added other things for the pack such as the Thaumcraft, Ars 2 and Buildcraft with no issues. Except still have 75% mushroomisland.

PS I'm using BiomeTweaker

Not funny.

AYFKM?! Necroposting in a 7 1/2 year old closed issue?

There's a mushroom island problem with BoP. MohawkyMagoo posted a fix for it in either the RTG or the CC threads a while back.

Here's the post where MohawkyMagoo explains how to resolve the BOP/Mushroom Island issues:

http://www.minecraftforum.net/forums/mapping-and-modding/minecraft-mods/2524489-realistic-terrain-generation-rtg-realistic-biomes?comment=1489

Good luck!