As many of you know, Filco Majestouch and CM QuickFire Rapid are made by Costar, and they share many similarities in shape and appearance. Filco Majestouch TKL and CM QFR are not the same, however, even down to the form and composition of the case plastic.
But--you can fit a CM QFR cover onto a Filco case, if you so desire--especially if you have picked up some QFR covers for GH's 6-year anniversary customization extravaganza and don't actually own a CM QFR but do own a Filco TKL (I've seen a few people in that position, including myself).
There are a few differences between the top covers and a few relatively simple modifications will make the QFR cover compatible.
First of all, to illustrate the differences, here are the undersides of Filco TKL and CM QFR:

I have marked the areas of interest. Namely, there's a plastic protrusion on the CM QFR case that needs to be cut off, because it will prevent the cover from fitting closely on a Filco. Secondly, CM QFR uses a mini-USB port for its cable, whereas Filco uses a proprietary internal connector, so the openings for cables are quite different. You need to do some filing to the CM cover to enlarge the opening until it fits over the protrusion in your Filco case that holds the cable.

Then you can use the thinnest drill that you have to make 2 tiny holes where Filco indicator LEDs come through. Using increasingly thicker diameter drill bits, increase the diameter of the holes to your liking. Drill at slow speed, and you won't crack the plastic--it's very soft and pliable.

Snip off the protruding part on the CM QFR cover to shorten it (this is the part where the top and bottom of a case would be held with a long screw covered with warranty sticker, but the location of the screw is different in a Filco case--so you'll just have to rely on tabs to keep the new top and bottom together).

Some cosmetic and structural differences between CM QFR and Filco Majestouch-2 TKL covers:


The Filco cover is thicker everywhere and the plastic is a lot harder and less flexible. The CM cover feels flimsy in comparison.
After you've done all those modifications, paint the case to smooth out any damage you may have done (and just to switch up your keyboard theme!)


And you're ready to put the new cover onto your Filco! (You *may* also need to file the 2 inner tabs along the inner front of the top cover. Mine just barely fit into the holes in the bottom case, as they were ever so slightly shifted with respect to each other.)
