I have seen some that just put a large diameter disc of semi rigid foam on the hub then let it float there. The internal pressure (I assumed) pushed it up to the disc of the cowl. Any motion was just sliding against the cowl. This way the seal to the hub was snug and did not have to absorb any misalignment or wiggle from start/stop. Like yours, my cowl is hard to get on, but I have developed a technique that might work. The disc design might allow easier cowl install/removal. I will send a picture when found again :roll eyes:
Keep it going Andy!