I would be careful with your pressure relief system, any blow-off trub in the pressure relief valve and you just made a nice bomb.
I believe Miller has a patent on this high-pressure lager system, I remember reading the patent in detail online somewhere, but I can't find the link now.
There was also a story of an experiment a professional brewer did of this type, it was in the New Brewer magazine a year or so ago. I believe their results showed a higher level of diacetyl than acceptable. You also cannot repitch the yeast due to the stress on the yeast when harvesting at this pressure.