Hello.  Okay I need your help.  I am trying to decide between the ARMS SIR #46 and the #50 Bi-level rail.  I want to mount an Aimpoint Comp ML2 on the SIR.  I already have the ARMS Aimpoint mount with the forward extending spacer.  Which SIR is best for this optic?  Is it better to mount the Aimpoint forward or rearward on the SIR?  Also, I know that the SIR comes with at least one side rail that has a sling attachment.  Do the SIR's have the same rail on the opposite side?  What I mean is do the SIR's have a side rail on each side?  I want to mount a Surefire M962 on the right side of the SIR and attach my SOP sling on the left.  Or is it possible to mount the M962 with throw lever mount on the bottom and still have enough room for a vertical grip?  If you can help me out with these questions that would be great.  Thank you