I recently made a trip to Kentucky from South Carolina. I parked for three days and my RV-7 tip up endured heavy rain off and on for a good 24 hours during the time it was parked outside on the ramp.
I intended to use tape to seal the front gap (small but still there) and the rear canopy overlap from water intrusion. I wanted the tape to be removable without leaving residue, so I considered the utility of painter's tape of some kind.
I was visiting family, but decided to check on the plane each day to verify my tie downs, control locks and canopy leaks. I elected not to use a canopy cover since there would be a lot of wind over the course of three days. I've seen cases where a canopy cover has scratched aircraft that were parked outside during storms. A canopy cover can prevent water from getting into the fuselage for a passing afternoon storm without worrying too much.
Because I use wax on my plane the tape didn't stick well on the canopy area. I use Plexus on the clear canopy which prevented the tape from sticking well to the rear canopy. I'm not sure a more robust tape would stick any better.
In the end I got a few drops of water in the fuselage and baggage area, but it dried out quickly when I opened up the canopy and gave it some warm air and sun.
I've seen the avionics cover that goes down under the canopy and I might get one of those eventually if my attempts to seal the front of the canopy are unsucessful. It takes any water that might get in and sheds it off to the sides to prevent contact with anything back there.
Flightline Interiors has such a cover for sale:
Instrument cooling concerns while under a fabric cover have cropped up on the forums here. I suppose there's benefits and drawbacks for every accessory. I mostly fly on sunny days and park in a hangar. Maybe tape is the best solution for occational rain storms while tied down outside.
I have some weather stipping from McMaster Carr that I intend to try. It has a 3M sticky side. There are so many types of weather stripping available so I may have to try a few different shapes and thicknesses to get it just right so the canopy still closes easily while being sealed. This is the harder part...