I have some of the same questions and I am most likely going to be installing a C2C in a 40 Breeder.
I saw one thread where he assembled the two pieces out of the tank and installed it as one piece. If you're using a good silicone/adhesive like Dow 795 or Momentive 108 from what I've been reading it should be fine. I used standard Aqueon silicone in my sump and it's holding great over a year later.
Here is that post in the thread:
http://www.reefcentral.com/forums/sh...7&postcount=17
My build will be getting under way soon and I have a thread in this section about my progress. Will be drilling the tank this week and maybe getting the glass installed.
Here's the link to my build if you're interested:
http://www.reefcentral.com/forums/sh....php?t=2363465