@taniwha Thanks for checking, I replaced the that dll with the one from http://taniwha.org/~bill/ModularFuelTanks_v5.12.1.zip
In the meantime, I found a bug, in Squad_structural.cfg only the old rocketNoseCone is defined, the new rocketNoseCone_v2 is missing.
I assume it's safe to duplicate the respective section there and change the name?