I've not built a tip-up 6-7-9, but reading this discussion made me curious about sealing the canopy skin gap. Seems like everybody is chasing the perfect rubber seal, but the automotive world generally avoids depending on rubber for water sealing in door openings, sunroofs, etc. Whenever possible, they use a channel to guide water where they want it; any adjacent rubber is for air sealing. Why not install a drain channel under the canopy gap, so that water is directed down to the longerons and overboard?
Two quick ideas, no dimensions, no details, just thought starters. The first is a glass/epoxy water channel across the gap between the bulkhead and the seal angle. The second is a formed metal strip; the channel is formed with one pass through a bead roller. It would shim the top forward skin up .016"; don't know if you can get away with it.