I've seen two VERY effective water sealing efforts on Speedsters that have both impressed me greatly:
1. Bruce Stumpp's use of Blue, Painter's, masking tape along the intersection of the top and the windshield. HIGHLY effective, seems impregnable to water intrusion (i.e.; the rain water doesn't deteriorate the tape smackumpucky stuff), easy to remove, completely eliminates any leaking along that edge, can take Interstate speeds in excess of 80 mph AND it leaves no residue when removed. You can also write "FEAR THIS!!" on it in Magic Marker, for the younger set. I used it on the last trip South for a stretch through South Carolina where we met HEAVY rains and it worked like a charm.
2. Hoss' SAW/SAS Cabriolet does not leak. Period. I've heard that other SAW/SAS's are pretty much the same. It's as if those cars come from another planet.... Next we'll be hearing that they have exotic, water-cooled power plants, effective hot water heat, air conditioning, hidden, power side windows and optional turbos and automatic transmissions.
What? They HAVE all that stuff??
See? I told you they were from another planet!!! No wonder it takes them so long to get here..... ;>)