Hi
I think that unfortunately there will be a problem using earmuffs with the CM7 and CM5 because of their "stick" design. Apart from the possibly reduced isolation where the "stick" part of the phones protude from the earmuffs, the position of the phones will be affected. I've found that the single bggest factor affecting the sound (the effect on the bass being the most obvious) of normal earphones is positioning, and I already find it difficult to position them optimally even under normal circumstances.
Long ago I tried using earmuffs with the MX-400 in the hope of avoiding the more costlier canalphone alternatives, but once the earmuffs touch them slightly (even the cords) the phones were moved from their original positions. I gave up and eventually ended up with the EX70, EX71, HJE50, and ER-4S .....
But earmuffs are more useable with (semi-?) canalphones of the EX71 genre since they are not so easily dislodged.
However, I'd be most interested if anyone does manage to find earmuffs to work with the CM7/CM5, as I also recently got hold of the CM7(Ti).
Talking about positioning, do you have any problem getting your CM7 to stay in place? I find that the most frustrating part about using them.
Cheers