[Stigoe]

I just haven't gotten around to replacing it yet. My mill is a G0704 and I am not sure that it could handle whittling down a chunk of steel that big. This is what I have in mind.

Do you think that using Aluminum would be acceptable?

I'm converting my WM290 (one step down from yours) and I have basically the same mill as you, and I managed to make a steel spacer, more or less. I didn't make it very elaborate, just a rectangular block, so your mill should be able to make something as well. Aluminium might work, but I would suggest to use steel.