I was going to put a small speed fin in my Glide last week to help speed it up and I'm sure it would have made some difference.
But sometimes a gain in one place means a loss somewhere else.
Coming from a windsurfing background I know that fins can make a huge diference..and I mean HUGE..

BTW.. I used a small 8 3/4" center fin on my 11'4" yesterday at the pines instead of the huge 10 1/2" stock fin.
Not so much for performance or speed but because it's so shallow and with a reef bottom..
Here's a pictures of the fin that Blane Chambers recommended that Rich use in his new 9'6" PSH and Rich said it made a big difference.
Fins aren't cheap but they're worth it trying different ones till you find one that you like.
DJ