Uh, I'm probably gonna get eat up for this but....why don't you just NOT shoot groups ? Pick up a five spot target and shoot 5 arrows at a time.
Having said that, I have shot 30x's for awhile now and I switched to Carbon Express pin knocks, they are much more durable imo. I also use the "baggie" method for the bushing and it works well if they need replaced.
Good luck and good shooting