Combat Jack is certainly right about what he says, but there are some folks here who do use a scope on the carry handle w/o too much trouble. The two main problems are eye relief--on anything that's very long, your face will end up at the back of the buttstock--and the height over the bore. You can't do anything for the latter, but choosing the right scope can minimize the eye relief problem.
Sticking to a short scope of 10" or so, and finding one that doesn't require 4" of eye relief, would be the best solution IF you can't afford an ACOG.
Burris makes a Fullfield II in 1.75x5 that's fairly short, and it's under $200 if you want to experiment. If you didn't like it, you could sell it in the EE and not take too much of a beating.
Also, Sightron has a fixed 4x S2 model that's only about 9" long, and only weighs 9oz...you might check into that one as well.
I don't have an ACOG, but I can see why it would be the ideal solution to the carry handle mount problem...but it does come with it's own problem, the "holy SHNIKIES is that thing expensive" problem.