i think your insane so much effort. did you actually look into the amount of "squash" the o-ring is meant to have to sustain certain pressures or it "extruding" while the tube was being installed, but then again its double o-ring so if one fails... suddenly machining down the ends of the tube sounds very appealing to me. i'd say its just the friction, but i dont think water cooling pumps churn out massive PSI's of pressure. OP have you considered just blanking off a piece of pipe and installing it into a fitting cranking up the pressure (maybe house mains pressure) and seeing how much they can cop before the tube blows out? purely just as a fun experiment?