There is a very high density of experienced pro's here:
www.m4carbine.net
That's another place where I would go with with this kind of question.
Might not hurt to consider a Daniel Defense Omega rail for a good combo of mounting simplicity ( 5-10 minutes ) , light wiegth , and rock steadiness.
Brownell's is likely to give you a military discount on the Omega and other gear that they carry.
You can never go wrong with Larue -- just ask them if the item fits your needs. The Vltor offset Scout light mount is hard to beat.
You need pro grade gear.