I have no experience with robot pneumatics systems, but I have built many air guns that I'll typically fill to 17 bar (limits of a cheap bike pump!), and I'd never trust a vessel with a large diametre like that, and just a tapped hole or something in one side. In the end of the bottle is different, the weakness is even, but in the side sounds like a disaster waiting to happen. Unless it's an entirely custom setup, welded into place, properly pressure tested, etc, I'd give the idea a wide berth.

In fact, unless it is common practice in the hobby, I'd avoid drilling into the bottom of the bottle too.