Like I said above, I recently looked at an SF.260 canopy, which is a fairly large expanse of Plexiglas, that uses a tubular frame like the RV's. The SF.260 canopy has rubber grommets as described above. If it's good enough technique for a production military trainer / light attack airplane, I don't think it can hurt on our RV's.
I know my canopy cracked aft of the passenger seat, near the horizontal brace that goes across the fuselage. I think Wingnut's cracked there as well. I've got a few other small cracks as well, mainly on the aft portion of the canopy.
RV-8 N88MJ (Built by Michael Robbins)