Don,
I like your drill press base better than the one I made. I really followed Larry Ms "If in doubt, build it stout." I think I over did it.
I did recess the base, just as you did because the DP is more than tall enough for my 5' 6". Also, as I remember, the head on the DP is something like 90#. If I were moving it and it started to go...it would go. The darn thing weighs about the same as I do.
Note the bolts that screw down to lift the base just off of the casters.
Basically I did what you did except I put my casters on outriggers. My footprint is too large for my shop. Don't be surprised if I copy you when, and it, I ever get time. I didn't even think of recessing the casters like you did. Dumb Guy Me.
Enjoy,
Jim