I don't know if these pictures ever made it here, but I sandwiched a DCM style freefloat tube inside some A1 handguards a few years back.
I don't really want to do this again as it involved a couple hours of fitting.
This is more to show YOU that it COULD be done if you were so-inclined.
The particular customer I did this for wanted a "sleeper" rifle, 1:8 twist heavy barrel that looked old and stock from the outside.
I love the flat bottom of the A1 handguards and my personal "utility" rifle is a 20" M16 clone.
With the heavy barrel, the rifle sits on your hand very nicely, like a DCM gun should.