We talked about different products for re-waterproofing Sunbrella this past Spring. I used 3M Scotchguard for Outdoor Fabrics, their heavy duty stuff. Sprayed the dodger, mainsail cover, suncover on the headsail, BBQ cover and binnacle cover. I washed the boat one last time just because over the weekend and I was really pleased to see that the water is still beading up on all the canvas. We had a huge amount of rain for the first part of the season, but the stuff seems to have held up well. I would buy it and use it again. I believe that it holds up much better than the more expensive 303 product. Of course, this is a pretty short term test. Although I wouldn't think the 3M product has any adverse effects on the Sunbrella fabric itself, I can't swear to it.
BTW, the Island Packet leaves this week. The new owner is taking the boat to another state via marine transport. The new home is an inland lake in Indiana.