Dear Madam,
You are right in approach that we make some assumptions when we have no firm data,which we should clearly mention in stress report, say in Caesar-II title page.

But we, as responsible engineers, are accountable for resonableness of these assumptions to our clients. In the case of engineered solution with bellows, bellow stiffness properties are important.

Fortunately, in the realm of metallic bellows, EJMA is there & there is uniformity of approach among major bellow vendors. In Caesar-II itself, we have a few bellow catalogue data. Bellow vendors are generally co-operative in finding out a right solution.

In case of rubber bellows, we expect same co-operations from bellow vendors

regards,

sam