Tool Grinder (maybe)

[f350ca]

This is the beginning of the housing, note the quarter round corners, not necessary but gives it that cast look, till I get a foundry going to actually cast something.
Of course the plate has a slight crown from welding, as expected so I was going to add the two pads sitting there then mill them off flat, one for the tool holder the other for the spindle.
Rather than weld just the outside, should I burn a big hole in the housing where they will sit then weld inside and out? Im leaning to that method, then the mounting bolts only need to be threaded through one layer or 1/4 plate. Any opinions welcomed.