...
It's known that high pressure oil seals work if done right, so I'd bin
that with the minor issues that can be solved later by throwing enough
money at them, ...

I'd wish - but lots of slightly different sizes - and you are going to
be able to find a seal for each diameter?

Maybe one could get a list of stock seal diameters, and find that yes,
the pressure and therefore test force you'd end up with would be just
fine - sits just where it needs to be to plot the S-N curve for
fatigue performance. Throwing aside minor vanities like getting the
stress which should mean the mean-average sample break is at exactly
250k cycles, etc.

Rich S