The slack portion between the platen and contact wheel works fine for a mild full-convex. YMMV depending on the belts you use. Removing the platen completely might make it too floppy. I don't know, try it.
I can't upload pics right now, but I'll try to describe it without confusing myself...
First, I removed the side plate completely. It's just held on by 2 thumbscrews.
I used a Dremel with a fiber cut-off wheel. Two cuts: 1 running parallel to the belt path, about 1/4" to the left of the contact wheel. The other cut is perpendicular to the belt path, at about the 1 o'clock position as you look at the contact wheel from the side. The cut-off wheel was a little too wide to get the cuts to meet without digging past where I wanted them to be, so I just got them as close as I could and broke the remaining 1/8" or so by hand. I suppose you could drill a 1/4" hole in that corner, cut towards the hole and it would look better. You could also cut more of the guard away, say back to the 3 o'clock position, but that didn't seem necessary.
That's it. It almost takes longer to describe than to do it. Just be careful not to slip and put a big ding in the contact wheel, that would be a drag.
The contact wheel works much faster than the platen for profiling, and saves wear and tear on the platen as well.
Two things I forgot to put in the diagram: I removed the handle on top because it was getting in the way. You can just grab the round thingy with your hand to take tension off for changing belts. I took the table off the belt portion and just use the disc sander or my "calibrated eyeball" for squaring things.
I mounted mine on the very right end of my bench, so the belt portion hangs over the edge. With a bucket of water under it. This saves a lot of cleanup time and helps prevent setting things on fire.