thanks! I like the top too, even though they cut the back corner hole too small.
the silicone is GE Silicone I in black. was hard to find. it has the nicest color underwater. not all glossy, kind of almost brown. they had bronze color too, and I found brown online, but local selection was limited and I'm using black substrate.
I didn't boil my cork. I wanted to, but I wasn't really set up to boil such large pieces, and I was rushing. I was also worried about premoistened cork adhering to the silicone. I did, however, really brush them hard with a stiff plastic brush, and now that everything is in place, I've been running warm chlorinated water through the tank with carbon in both filters and with an extra pump (with uv sterilizer) for fast circulation, and spent a good 2 hours yesterday brushing off dust and debris, and blowing a powerhead through all the nooks and crannies with a hose. all in all, I'm not so worried. from the last tank I know that the shrimp and snails love the cork's natural stuffs.