I don't do a lot of customs, but I remember taking that tiny screw out the first time I repaired an O-ring.  When I was younger I would change pants when someone had an accident and joined the BCB (Broken Crotch Brigade).   

  Lost thumbs would only bother me when they were a favorite, and they didn't happen that often.  As long as they had one thumb, they could hold a weapon and the "damaged" hand could be posed toward holding the clip.
I swap out heads and switch parts around, mostly to give current characters a wardrobe update, but occasionally to create a new character.  I'm not too much into painting/dremeling. 
Although I did do a badly wounded soldier that I will post some day.  He's a mess though, probably would rate him PG-13.  I feel disturbed when I see him.  
