Sorry I was on vacation and didn't see this all come up. I did make a mistake in hearing the sales rep call the spring a K-11 when he called it from the shelf.
THE SPRING TO USE IS A RW-11.
I confirmed that with him this morning when looking to purchase more. He came back with the spring that JustSomeBob and a few others smartly pointed that it wouldn't fit. You are right a K-11 wouldn't fit in there.
Have those new springs come in yet for you to test? I don't see how to order the RW-11 since I live in WA and do not have access to your local store. But the 9637532 I can access, but want to know first if they do indeed work well.