Looking for opinions.

my 240 cracked in the end panel near one of the upper corners, diagonally toward the center of the end face. The crack traveled to a bulkhead hole and stopped but I don't trust it.

I've read a few websites that say you can cut the silicon with a razor blade and remove the panel, clean things up, and glue in another panel. This sounds good. While the tank is removed from it's base I'll double check it for flatness...

I have two concernes about the gluing process I was wondering if any of you gurus can address.

1. The Dap Aquarium sealant says 100 percent silicon. Everybody says use 100% silicon. This particular tube says not for aquariums over 30 gallons nor for water depth over 18 inches. Is there a better choice locally? I doubt aquarium volume is important but my height is 24 inches.

2. They say silicon doesn't stick to silicon. But multiple sites say to just scrape the glass with a razor blade to clean the old silicon off. I'm concerned about leaving any residue, and then having a bad joint. Can I chemically strip it with anything?

Thanks,
Jack