I was just looking at water between the rails on Becky yesterday...
While I don't share the OCD approach of the OP, I do wonder why there are no drainage channels to let the water out.
When I was doing a lot of motorcycle touring on my BMW R80/7 and R100S, I deployed a repurposed strip of ripstop tenting material from a cheap tent that got a hole burned in it by a campfire. I made a stip a little wider than the seat and as long as the bike from the handlebars to the top box. The front end was shaped for having the wheel in the locked position. I incorporated nylon tape in the long side seams to fix it to the bike.
When I settled the bike after a ride, would roll out the protector and suspend it over the length of the bike, tying the tapes to the mirror stalks and the rear luggage rack. It clearly was not good enough for a decent Highveld thunderstorm, but it was most effective against the heavy overnight dew we get on colder evenings and mornings. In the morning, my camp mates would be out drying off the seats to their bikes, while mine was dry to start with.
The dew strip rolled upto about 40cm (18") wide and 7cm (3") thick. If I were to make one again, I would compact it by putting ties in the short end seams only, as the long side seams took up the bulk of the volume when packed.
Sorry, no pics of my little dew protector...
If I were to make one for the Vespa, I would probably use a diamond shape with two opposite points cut off. With ties in the two ends over the bars and rear rack or topbox, the pointed ends could have ties to secure it under the belly to prevent wind taking it away.
⚠️ Last edited by Fudmucker on UTC; edited 2 times