There seems to be some conflicting advice about the hole size. Logic says, as you do, that the hole only needs to be big enough, whereas a Stans video suggests you file the edges down (for a better seating, I guess).
I've found the best approach to making the valve hole in the tape is to heat up a crosshead screwdriver over the flame of the gas range and then use this as a hot poker to melt a hole in the tape through the valve hole.
Thanks for the tips, i’ll See what happens with a different valve.