The best seven cell action I saw was Ray Wood and Tony Stott running the then just released Tamiya Porsche 959 with seven cells at the Hornsby track during the lunch break
....DAMnnnnnnnnnnnnnn that thing was ballistic.....
I remember Ray's boomerang running the 7 cell "international" class as it was called. The class did not live long - but it was sure spectacular. I seem to remember almost a couple of heats of it at St Ives clubbies?
Still, I often wondered how you made those gearboxes last
Cheers
Darryn