This is the ARMS # 16A for Aimpoint. It's the only mount I know of that will facilitate an Aimpoint in a carry handle.
[url="http://www.hunt101.com/?p=78990&c=500&z=1"][img]http://www.hunt101.com/img/078990.jpg[/img][/url]
its sligtly higher than an aimpoint on a Flattop/sir, but its a great 1 piece design, other designs, like the ARMS #2 and their #22M68 will add cost and height.
[url="http://www.hunt101.com/?p=78995&c=500&z=1"][img]http://www.hunt101.com/img/078995.jpg[/img][/url]
The ARMS # 22M68 sits on a #38 Swan Sleeve, and a SIR, and a KAC RAS 2 at the perfect ht. as is, while co-witnessing the dot w/ your sights.
[url="http://www.hunt101.com/?p=79001&c=500&z=1"][img]http://www.hunt101.com/img/079001.jpg[/img][/url]
The full spacer will co-witness your dot w/o a rail of any kind when the #22M68 is mounted w/ an M2 directly to the flattop.
[url="http://www.hunt101.com/?p=78993&c=500&z=1"][img]http://www.hunt101.com/img/078993.bmp[/img][/url]
The half spacer, I'm not sure of, to be honest, never saw a need, but others will know.
There are other Aimpoint mounts. The ARMS cantilever/spacer is shown in the first post it will mount your sight forward and high enough to co-witness w/ the BUIS.
There's also KAC mounts, PRI and GGG moounts made for the Aimpoints but I'm not familiar w/ those so I offered what I could.
Lots of luck.
Hope it helps.
/S2