Hehe, somehow missed the discussions in this thread. I'm the guy Chuck was referring to with the DIY Line-X job. I drew inspiration from the Phenix bags after borrowing a friend's and being impressed with the Line-X there. One of the biggest pains, I've found with golfing in wet weather, is how wet your bag gets from sitting on the ground--no matter how much you protect it with the umbrella, water still wicks up from the wet grass and mud. When I tried out my friend's Phenix bag, I was surprised at how much drier everything stayed from the bottom protection. So, I decided to try to do it myself on my Simian:
I was planning on posting about this eventually, in a different thread. I still plan to, but there's a quick look at my amateur application. Results so far are good. With the way the Simian is set up, you don't have to worry about your discs getting wet from the bottom, but the pockets stay dry now as well. And of course, there's an extra layer of protection which should only serve to prolong the life of the bag (especially since I'm betting it will wear more quickly having me sitting on it all the time.) An added bonus is that it gives the pockets and bottle holders more rigidity, so the pockets/holders are less prone to swaying around while walking. I was worried that it'd weigh the bag down, but I didn't notice any significant difference.
The stuff I used was
Grizzly Grip, a pint is plenty and it should cost somewhere in the neighborhood of $20 (the shipping cost is pretty high due to regulations on chemicals and such).