some general concepts about pressure vessels from my former life.
1. a vessel can withstand increased pressure as its wall thickness goes up. (same diameter cylinder with bigger wall will do better)
2. a vessel can withstand increased pressure as its radius drops (smaller diameter cylinder with same wall thickness will do better)
3. a cylinder is better than a square and a sphere is better than a cylinder. pressure is distributed against the wall perpendicular to the wall. this causes increased stress at corners.
4. pressure test with liquid and not gas. the stored energy in a liquid will dissipate quickly in a failure while that of a compressed gas does not