Nope,how many kits you want to use is up to you.I'm using triplets because triplets are in the logo, and if I use one in the give away I still have a set of twins to sell. I tried about a year ago to do four kits at one time and that was to hard, I kept getting limbs mixed up. 3 is enough for me. When I choose my kits I try to get sculps that look good together,similar features and size. I like using one closed eye and one open,but that's all up to you. :bigsmile