If you haven’t already, you may also want to look at @gero’s design that puts the belt at the bottom of the c-channel. The nice thing about that setup is that you can easily utilize the whole travel of the c-channel axis. With mine, I lose nearly an inch at the bottom with my current router mount. I am thinking I will redesign the mount to be able to utilize that travel… unless I switch to a spindle which may make that issue moot. Ideally, I want my collet to bottom out at z-zero to allow use of the whole bit.
That is another bonus of @gero’s design in that at the top of travel, the collet should be above the ring to make bit changes easier. As mine is set up, I am able to change the bit without removing the router from the sled, or the sled from the work piece, but it does take a little finesse.
I also like that the vacuum system could potentially run underneath, and that it is less likely to accumulate chips in the c-channel. This last may not be as much of an issue as I fear, though. And a vacuum system would also serve to mitigate the chip issue. I am planning to pipe in some 3/4" loc-line from the vacuum hose.
The only drawback I see is that it moved the CG of the z-axis away from the work surface.
Edit finally found the post that I was thinking of showing @gero’s setup: