I'm not sure as to why people assumed I used my lathe cutting bit to cut all the way down to the rim surface? Look back at my original post
. I used the lathe cutter to bring the foam down to 2-3 mm, and then used sandpaper (coarse and fine grit) to remove the remaining foam.
I'll admit, at first I did try using the lathe cutter to true all the way down to the rim. The rim deforms and the cut is not perfect, simply put, it doesn't work. But, the above method with sandpaper works like a charm.
As for the truer, it cuts in a perfectly straight line and is not walking into or away from the rim. I tested this by using a machining dial indicator and there's no problem.
I'll give the acetone method a try another time.
Thanks again for your wealth of information.