@El_Cheapo Welcome back, Neil.
There are pros and cons to both installations. I chose to mount the LM feet on slats of 3/4" MDF so that I get the most Z travel possible. The initial big plus for me was squaring my LM. The MDF slats have slots in them. I used 1/4" bolts up from my table base and through those slots. When I was squaring my LM, it was a simple matter to loosen the bolts, nudge the slat a bit and tighten it back down. This made it very easy to move the Y gantries a very small amount.
If you ever plan to add the Vortex rotary to your set up, you want to mount your feet high. You will need all the Z travel you can get.
Finally for those jobs where I am using a short 1/8" mill to cut the parts out, I put another piece of MDF under the parts to enable the bit cut all the way through.