I do not own a 503 but alot of camera's use a flocking material. Are there any telescope shops in your area? This is used in the tubes to prevent stray light. I use a good grade of contact cement to apply. Recently reflocked a Mamiya 645 & Kiev 60. Good luck, Steven.
Snederhiser, how did you get the old palpas/flock (high density foam) off ? with a scraper?