Okay... a small update.
The boot was removed last Monday at about 5:00p and I thought I'd spend the following Tuesday in the tank. That was absolute crazy talk.
Just taking a few steps for the first few days was enough excitement and the gyrations req'd to climb up a step ladder and slither myself over the top of that tank were out of the question however, todays the sixth day and I spent it in the tank. All the substrate's gone, I removed the silicone in one giant piece and I suspect I may have identified the problem... maybe.
I found a spot along the bottom silicone seam that had Peace River gravel behind it (between the glass and the sealant) and a hole in the silicone that would have been my error in not noticing it when I did the job last time. If you look directly at it there's no obvious hole but if I were able to look up from beneath I'd be able to see a void in the sealant that is sort of like a vein in that it's not a straight line from inside the tank to the outside of the tank but it's there and it's the only thing I saw that seemed suspect. Odd that it took a couple years to actually leak but whatever; it's done.
Now there's a ton of razor blade and acetone work to do. I don't mind the razor but that acetone is some tough stuff.
I'll be done w/ all that by next weekend and hope to complete the re-caulk then.
What was a fairly tidy room and a beautiful tank have both been a horror for the last couple months. Can't wait to get this done!