Based on the recommendation of a club member who owns a Sport Coupe (as I do), I bought this:
https://www.amazon.com/Raggtopp-Fabr...xpY2s9dHJ1ZQ==
The cleaner part seemed to be somewhat effective, but I'm not sure that it was any better than the regular car wash detergent I use. The "Protectant" (waterproofing) does seem to help a lot. Previously, when driving in the rain for a while (maybe 30 minutes depending on how hard its raining), I could see that the canvas was wet on the inside. I haven't seen that since applying the product and driveing several times in pretty good rain. Note that with the bottle of protectant supplied, I was able to put on a good three coats.