Dear Friedrich,
I think the error is that you’ve specified that there are 30 airfoil files (NumFoil = 30), but you’ve only identified 4 of them. Perhaps you want to set NumFoil = 4?
That said, you shouldn’t need to convert a model into FAST v7 format in order to get calculate the moments of inertia of the RNA. You can use the linearization functionality in newer versions of FAST/OpenFAST for that. The FAST v8 and OpenFAST linearizations do not show the mass matrix directly, but this matrix can often be inferred from other matrices generated through the linearization process. A similar question was asked and answered in the following forum topic: OpenFast 2nd order Linearization - #2 by Jason.Jonkman.
Best regards,