Can anyone pull up some seal photos or photos of the embodiment please?
Even if the pressure seems to increase the sealing Chris the resulting loads on the elastomer could be too high and eventually fail the seal through excess friction, temperature, lubrication exclusion etc. I am not 100% familiar with the embodiment though so can't accurately contribute right now.
If I see some parts/photos/images/illustations etc I may be able to help - this kind of sealing scenario is relatively simple (although I'm by no means saying it's trivial) compared to some of the sealing designs I have been heavily involved in.