This thread is 8 years old, so not sure why it showed up in my feed! But I will add for those searching for information that some vets like to wait longer not because they feel uncomfortable doing smaller animals, but because they like to let the *** hormones contribute to the proper growth of bones and muscle as long as possible. Cutting off these hormones too soon could lead to weaker bones and osteoporosis later in life, and rabbits' bones are already lighter and less dense than cats' and dogs'.
I've had several dwarf boys neutered (shortly after testicle drop), but waited till 9 months for my dwarf girl as she was malnourished and underweight when I got her. I think body tone and health is more important than some fixed weight threshold, though I have heard the 2 pound "rule" for bunnies as well.
This article is great for those looking for info on spays and neuters:
http://www.bio.miami.edu/hare/opcare.html