I honestly can’t give you a definite answer, but what I understand is that the max the M4 can reach is about 11x11. I think I read that the belts are about 14 ft long and you can deduct 1/2 of the diameter of the sled.
So, it seems like you can reuse the frame you have with a few modifications. I think the vacuum system you are using would still work. Depending on what computer you were using before, that will probably still work for the new M4 as well.
12x6 is the distance between the anchor points? That should work great @Dieseltim is exactly correct.
Unfortunately the R22002 is too big for the Maslow4. When we relied on gravity the extra weight was a bonus, but now that we don’t need gravity anymore the lighter smaller router is better.