Hi Desert,
Sadly, Mr Druine is dead. If he wasn't, I'd happily pass his contact details on to you as I'm sure he'd welcome your technical views on this matter. As it stands, his design is well proven, so we feel quite happy to go along with it.
The fuel tank in my Cub is in exactly the same place too. Mr Piper built a few Cubs with such fuel tank locations, so we feel reasonably happy that it'll be ok.
