Having return edges isn`t mandatory and that goes for the entire armor, however they contribute of giving the armor a sence of thickness and if one plan on using screen accurate strapping they are almost a must in the torso, for higher levels of accuracy - Centurion - there can't be any on the wrist-ends of forearms...so it's about personal preference. My advise if you cut the neck line is to not make a new return unless you really want to, no one will see it anyways...and as Christine said, a bath and strapping will aid the butt-issue and adding on the thighs would make it less apparent...and one final note: check Christine aka Crickets thread on how she did her RS-kit - it's a great read