Yes, we're using Sylgard, but I'm not thrilled with it. It tends to form cloudy spots and erode where the light hits it repeatedly. So I'd love to hear about optically clear silicone rubber alternatives that were more robust. There are also issues that arise when you coat the tank where the glue joints are - Sylgard is a platinum-cure silicone, which means that it's not only expensive but it's very touchy about what it will cure next to. Other types of rubber can inhibit the cure, leaving you with sticky areas in the PDMS. So if you're trying to work out an alternative vat, I'd strongly urge you to test the Sylgard up against whatever silicone caulk you plan to use before committing a lot of time and materials.

Andrew Werby
Juxtamorph.com