Very good writeup on the tank mods! I prefer to use the 2nd method and retain the nipple.

I had a lot of tank issues at PNB but so did everyone else. A couple of the jumps had a very narrow window to hit the downslopes in and overshooting at all was a 20ft drop onto flat. Specifically I know Kyosho tanks had issues and I heard a lot of Mugen tanks cracked too. With that said the Tekno tanks are definitely made of the wrong material. They are simply too weak for offroad. I went through the exact same thing when I ran for Mugen and the MBX7 came out. With these being the first nitro cars Tekno has produced I completely understand issues like this.

Keep in mind Tekno has a new tank coming out shortly which I witnessed hold up to major abuse at PNB. It is a lot stronger and I believe has the clunk issue resolved. In the meantime, there are a few things you can do to strengthen the current tanks:

Boil the tank to soften the plastic slightly.
Shoe-Goo the mounting tabs to slightly reinforce.
Place foam underneath tank.
Ream tank mount holes so bolt can slide through without having to be screwed in.
Place 2 o-rings underneath each mounting tab for more cushion and to slightly raise tank from chassis.

You want the tank to have a little movement but be secure enough that it doesn't break off of the mounting tabs or smack the chassis hard enough to crack.