It doesn't matter how far the silicone comes out, regardless of tank size, what matters is what is in between the glass. Greg should be able to do it tidily, but it may add to the cost as it would probably need to be masked to prevent it from being smeared all over the glass like they do with the clear [which turns ugly and white] stuff, you want a nice straight edge as it will be more visible, but still better looking IMO. I'm going to go black with my next tank, I hate the way old white silicone looks!
Good luck selling the breeding set up, hope to see some action soon, would be cool to have three 1000L+ builds taking place at the same time (you, myself and Henward).