They will physically mount, but there is a pronounced overlap where the side of the M4 style meets up with the side of the carbine style. Here's 2000 words showing the M4 profile on the bottom, and the carbine profile on the top:
I've got a similar setup, an OKO on a CAV Arms forward mount on an A2 upper. I used the CAV Arms M4 handguards, and machined the very top down an 1/8 of an inch or so to provide the necessary clearance. Only to the 8th rib forward though, so the handguard looks untouched but the unseen part under the mount doesn't make contact with the mount at all.
Depending on what sight you're planning to use, CAV Arms also makes a forward mount now that sits a little higher- just enough to clear their M4 style handguards...