Hi Ken,
That is something I had considered in relation to doing 3D shaping on the edges of the sheet. If the side rails were fixed and the Home/Zero point was accurate enough, this might work.
I think though that if I can get a bit that has a cutting edge the is ~2.125-2.25" long and if the gantry can be modified to get the Z-axis motion up to ~2.375-2.5" then that would be easier and more accurate.
At this point, I think my controller board has a fatal flaw in the X-axis channel, and I need to buy the 10A version of the board:
(click on image for link)
The plate underneath is the heatsink.
The stock board is rated at 2.5A, and the cooling for the output stage is much less robust:
(click on image for link)
My board has heatsinks with less surface area, though they did not get very warm either.