I agree with Bob's suggestion, Mark. If that doesn't work for you maybe you can find a small trim saw with a 3-4" blade to do the job. One rather radical method you might consider is tilting your circular saw at a 45 bevel and see if you can then reach what you want to do. The mating strips would then need the same angle of course. Heck, maybe you need to buy a trim saw AND tilt IT at 45 bevel!

Half of communication is listening. You can't listen with your mouth.