120 extra tall back replacement and seal

[Kevin Burke]

Hello everyone.
I bought a used 120 extra tall (10mm glass). Got it home, planned to have it resealed, and discovered an internal rock ding near the middle of the rear panel. Very small (1mm) but can see a tiny crack radiating from the chip.
So, off to replace the back panel.
Got the trim removed (@#$%^$#!!!) and find the bottom is 5mm glass. A label says it's tempered but I can find no tempering mark and the lcd/polarized glasses test says it isn't tempered.
Seems awfully thin to my inexperienced eyes.
I can't find (google searches) info on bottom thickness requirements. The tank will be thoroughly eurobraced.
Any advice?
Thanks for your time. Kevin

 

[Ulu]

I wouldn't try to replace one panel. You will have seepage.

 

[Kevin Burke]

Thanks, Ulu.
The plan is to remove the chipped panel. Clean all seams so only the structural silicone is left. Replace the panel, let it cure, then reseal the entire tank.
I've recently learned that the structural and sealing silicone can be done separately.

 

[Ulu]

That would definitely be better.
And I have done it that way.

Silicone is silicon plus polymers. And other things.
The polymers can vary a lot.

I expect to eventually have seepage.