Mig welding near gas tank?

Planning out the rollbar for my $2016 challenge Miata. Have Mig welded before but never on a car. Locations for mounting plates are going to need to be near each corner of the gas tank. So what do you do in this situation? Obvious draining should be involved, but I don't see how I can get every last bit of gas and the associated vapors out.

Thanks, Justin

In reply to Jah29:

Take it out of the way, or use a heat shield and fill it to the top. There are less vapors in a full tank than an empty one.

Pull it. Gas tank explosion sucks. I got really lucky last time.

If you're gonna leave it in it's safer full than it is empty.

If you have the choice, TIG is better because it doesn't throw them glowin' balls-O-far. As was said above, fumes are the true danger; fill the tank to the top with gas or an inert gas such as CO2 or argon (TIG shielding gas).

Full is safer. Do have friend with CO2 extinguisher standing by. Shield tank with welding blanket or sheet-metal.

I have been known to be a little reckless or careless over the years, but in a situation such as this, and taking into account Murphy's Law, drop the tank and get it out of the way. Unless it's just too much of a pita. Picture the worst case scenario and then do what it takes to avoid that. On occasion, I have filled a tank full of water and done some welding, eliminates risk, but more effort is involved.

Thanks for all the advice. I will not weld on the car without removing the fuel tank. It just occurred to me that I could build my own bolt in cage and that might be easier than dropping the tank.