I tend to a agree with the 90%...

I reckon if the spindle on there, or the one I made, can support a big enough fly cutter I can easily get over both sides by moving the spindle to either side of the Z-axis especially since 2" wide around the border will be occupied by the aluminium angle unless I mill that down. The problem then is maintaining an accurate height between passes, but that shouldn't be too bad. On the previous bed it was very handy having the ridge left from surfacing for a parallel reference