Sorry, I think it's a bad idea.
Two reasons - you say your weakest mark is in submission and obedience. I would not advance in levels until that improves. Doesn't mean you can't school more advanced movements at home, but I would not consider advancing up a level until you could ride a solid test with a score in the mid 60s and a good collective mark for submission and obedience.
Second, the stretchy circle, as you call it, is there in the test for a very specific reason, and that reason is as a test/check of your training. It's meant to expose holes in the foundation. Your response indicates that you have some holes in the foundation. If your horse quits/wanders when you feed rein to him, among other things, it means he's not sufficiently in front of your leg, and that you can't ride him from seat and leg. It may also mean his frame is produced front to back rather than back to front. And that he may not truly be stretching down in the long and low, but just doing what an instructor of mine called "Joe Hunter" - lowering the head but not using the back. Or in your case, Joe Western Pleasure.
So I would stay right where you are until you've really mastered stretching and a long and low warmup, and until you can ride on a long rein without losing the horse's focus and attention.