Hi all !
I glued yesterday evening my big tang, following Scolley's and Wendle's advices

!
The tank is 136x59x57 (cm) or for you american friends 53x23x22"
Glass thickness 12.5mm (1/2 inch)
Polished and beveled edges.
No braces (at least until I fill it and measure deflection of front and back panels.....will see)
Following Scolley's advice I used a LOT of acetone to clean...
Following my own wish to make final cleaning more difficult I didn't mask anything...
Following Wendle's advice, the bottom panel is inside the front/back/sides panels.
I smoothened the bottom seals with wet finger.
I made the vertical seams very small with a credit card (expired

)
I used 3 silicone tubes of 310 ml (I had bought 8, just in case...

)
All in all, the process took less than 45 minutes...
It seemed to me very easy to do it like that ( it was my first DIY tank).
I will post pictures as soon as I get my DSL connection back
I will update on watertightness after 3 or 4 weeks as I am going on leave, I guess silicone will have enough time to cure
Thank you all for sharing your experiences, that helped me a lot....
Now the adventure begins !
Sietch