Looking at the pic closer, why can't you just put a socket on the "outter" bolt? If it's rounded get a bolt remover kit from sears for 19.99. I'm kinda confused on the whole inner bolt outter thing. My sliders are held in with a single 10mm bolt that goes right into the frame. Or through the frame into the engine? (01 F4i)

 

Im a little confused too lol try to go into paint and draw a simple picture of it lol that will give us a better idea.