You are right, it ideally would vent out, in this case, VENT BACK INTO the engine. That is where the overpressure valve is situated on this machine. What I am saying is why rely on INTERLOCKS (Interlocks 1. A mechanical device that prevents a component from functioning when another component is functioning or situated in a particular way) such as an overpressure relief valve when ideally it shouldn't ever need to be used, therefore there is a possibility that it is frozen/seized or could have the inability to open all the way upon the pressure being high. I know, unlikey considering it is always lubed on atleast one side, but probable. I myself wouldn't want to risk it. A 400EX has pretty much an identical system, and I have seen a few of those blow seals. You can put a 100 GALLON tank on it, (I know you were exaggerating here as just the sheer pressure of the 100 gals would overwhelm it) but you would still need a sufficient volume of space for the oil returning to the tank to come into.
Now with everything said, if it is just a tad over the mark I wouldn't worry about it. But if it is more than that, I would definately take it out. And AV8R, I think you will find it amusing that I looked up a word HAHA. It is so you wouldn't for Hayden LOL.