Following is a more detailed write-up on the canopy seal mod. for the RV-8. Feel free to add any comments or ideas to make it better or more applicable to other RVs besides the 8 or 4.
Since the 8 (and other RVs) have had issues with the cold air on the back of the neck, I came up with a canopy seal that is a real option because of the expanding and contracting of the fiberglass and aluminum to cover the gap year round (in an inexpensive way).
It basically is a mini shock bike pump that racers use that has a quick blow CO2 cartridge connection (that I did not use). The pump is manufactured by Bontrager, and is called the Air Rush Road Pump (retails for $34.99 http://bontrager.com/model/07331
was purchased from a local bike store). I located it on the left side of the canopy, and it has a twist knob on the end that holds air if tightened, and releases it if I twist it counter clockwise. That is the key because it allows the inner tube to hold the air while in flight. I cut a small inner tube valve (from an old tire at the bike store) and permanently screwed it into the adapter on the pump. The valve on an 18mm tube fits perfect.
I then connected a small vacuum tube that I picked up at an auto parts store to this valve stem. I put some sealant around the threads of the valve stem and just ?screwed? the vacuum tube over the stem and it formed an airtight seal. I then ran the tube through the existing bottom canopy support out the back to an 18mm bike inner tube (smallest I could find). I did have to drill a small hole (the diameter of the vacuum tube) toward the rear of the canopy support to allow for the vacuum tube to exit and connect to the inner tube valve.
I picked up some soft stretchable fabric (like thin spandex) from Hancock Fabrics (soft and wouldn't scratch the paint). I begged my wife to sew the soft velcro to this "housing" so the inner tube would free float inside the fabric tube. This allows the inner tube to expand and contract when pumping it with no issues. Then I attached the other velcro to the inside of the skirt so it would hold this stretchable housing with the tube inside it. The Velcro had a sticky side to it and was attached to the inside of the fiberglass canopy skirt.
The length of the inner tube is whatever you want to make it. The valve of the inner tube had to be placed about a foot from the canopy frame exit. The reason for this is because there was too tight of a clearance between the turtle deck and canopy if it were mounted any more forward. I used a tie wrap on a sticky tie wrap holder to secure the valvestem/vacuum tube assembly. I cut the ends of the inner tube to the desired length and used clamps to temporarily hold the folded over ends while the innertube cement cured and formed nonleaking ends.
My canopy without the seal is pretty tight, but I had my youngest shine a flashlight and blow compressed air from the outside when I was feeling/looking around from the inside, and it appears to work great. He never felt any drafts when he was my first passenger. The real results will be best proven in the winter, but it should work fine. Six short pumps before takeoff just after I close the canopy, and that's it. When I land, I turn the small knob counterclockwise to release the pressure. If I forget to do this, it still opens and is no problem.