I've always mashed the pumpkin and it works great. I actually use banana squash because it's available at the store, fresh. Mashing does gives you flavor, but it can slow down the sparge and lauter. I batch sparge my brews and don't use any rice hulls, and I have not had problems yet, keeping in mind that I use a copper manifold. I would probably recommend hulls to a brewer who uses a false bottom though. The key is a good mash out temp and slow, steady lautering so you dont end up with a stuck mash.