The REAL practical difference between 30 and 50 amp is simply that with 50 amp you can run both a/c units at the same time...while with 30, you cannot.
I strongly suggest you read your owners' manual. 30 AMP power but 2 a/c units on the roof?
Is there a automatic switchbox that can run 1 a/c unit for awhile then change over to the other one?
Or maybe one a/c unit runs on shore power and the other via the generator? That sounds kind of inconvienient...or strange (BAD/STUPID) engineering...as a typical 55 amp generator can run just about everything at the same time....