Well, I decided to see how big it looked without the lid.
Much better. I was confident I could slip in and out of the tank via this manhole. Now on to sealing the seams at the bottom of the tank. There were some really mangled bits (remember our tank that went a-flying through the night?) and they received an extra layer of the waterproof bitumen rubber. This was easy to apply, didn't smell (important inside a tank) and dried very quickly.
I did 4 layers on the bottom half of the tank (gnomes are small and can't stretch to 3 metres). The next day we rolled the tank so that we could do the other half of the tank.
But I was soooo sore after all this climbing in and out I only did one more round next day. The rest of the layers were left to the Flower Gnome.
This is the inside of the tank after a layer or two.
Fingers crossed that this tank is now completely sealed and ready to hold all the water that is supposed to flow in during winter.