Will take a look into the relevant literature that I have tomorrow.
Did you already check out "Der 30,5 cm Mörser: Österreich-Ungarns berühmtes Belagerungsgeschütz" by Christian Ortner?
It could be the ideal starting point if you don't shy away from german language.
Would be more than happy to share my copy with you, if it helps to push this great project forward.
I feel already sorry for this anticipatory nagging, but please make sure that any of your upcoming artillery kits (especially such heavy & highly complex ones as the type in question) will be done in "hard plastic"!