Just had to deal with one of these bolts today. Glad I was smart enough to check the forums here first. Completed my first two keystone battery mods ever today (Blue Marvel Super Heroes and Green Super Street Fighter II) and several hours today I'm still up and running!
Easiest way to remove the damn 'C' bolt is to keep the bottom part held w/ a screwdriver and drill out the top. Never encountered an A board with one of these until now.