a8 Well I guess a tablesaw is better for the job of cutting the kerfs. If your going with Chazmt's method (and you may already know this) you can just cut the foam with a saw and then sneak up to your line with homemade sled like this and get a perfect angle. This is one for 90 degrees but with a simple spacer you can make any angle you want.
Just in case someone is interested in what can be done if they have a tablesaw and at the risk of going too far on your thread I thought I would post a few more pics.
1" foam around a coffee mug ( 1 3/4" radius )
Throat plate splitter
