I don't like rupture diaphragms for a number of reasons. What I've seen in my short and uneventful life is that if you have an unstable process, you will pop the diaphragms repeatedly. What then happens is the user uses progressively thicker and thicker diaphragms until you lose any protection you have. The only time I ever used rupture diaphragms was in conjunction with a relief valve when zero leakage was necessary or as protection as a last resort.

Rupture diaphragms are not precision devices like a spring loaded relief. I've seen test results on identical rupture discs and the simple ones without a cutting bar failed in a range,not at the same pressure. Have you got a picture of your current arrangement? There have to be other options.