We upholster many, many boats here and sometimes run into plastic substrates that just don't want to take a staple. Lots of Master Craft aft seats and some Magic tunnel boats use either fiberglass reinforced polyester resin or equally brittle stuff, Some one has stapled this stuff when these boats were made but we have very little success in doing that. Does anyone have experience with chisel point or divergent point staples in these types of materials? And just to weed out some questions, I do use a pneumatic stapler and stainless steel staples and am NOT referring to HDPE, PVC, or ABS type plastics.