Building my first flatop M4gery. Mounted the GG&G rear flipup sight today. Seems with the taller M4 handguard an Eotech would have to sit back to not run into the hanguard. Would I need to mount a GG&G Fire Rail GS-1 with the flip up sight mounted on the rail as well?

Seems you would want the MAD sight and Eotech at the same height to still use the iron sights. I know for the Aimpoint you want the MAD sight mounted lower than the Aimpoint for use of the iron sights.

btt

Cmone, how about some advice?

I am lonely

A fellow officer is running his AR15 in the way you described.  He has had no problems with his, I run a similar setup but use the A2 style backup iron sight from GG&G.  

I can't see where this would be a problem for you.  Neither of us use the firerail setup.

With an EOTech you wouldn't need any additional rail to have the optic co-witness with you back up iron.  for your set up, the EOTech is fine on the receiver, which is where EOTech is designed for. and with the Optic on your flat top rail, your MAD should pop up right in the middle of the window and line up with your front post.  

Hope this helps.