I just put one on my A2 and when I go to tighten it down with the retention nut it only goes on so far and the attachment bolt spins. what tool do you need to use on the top of the bolt to be able to tighten the nut down. I've looked at the top of the mounting bolt  and it doesn't look like it takes a screwdrivew, allen wrench etc. Also when you set up the Eotech is it better to set up the reticle
directly in line with the iron sights or above them using the  BC-Cam adjustment.

Thanks
Paul