Very interesting thread on here.
The difference between Stock and Mod really isn't that big anymore.
The same is true for Europe.
In Germany for example it's 5cell Nimh in both of the classes with the stock class having a 9.5t limit and modified running 3,5t/6t delta/5t delta something around that. On small tracks, like the German Nats this year it happened from time to time that Stock was faster/just as fast as Mod.
In the Uk, mod is 5cell open/ lipo 6,5t with most people using 5cell when runtime was no issue. Stock is 10.5/lipo.
The Eu went from 6 to 5cells 3 years ago I think and that was prett much the best step.
Modified became more attractive and much more controlable
I personally think lower voltage definately helps but, 1s is not really an option.
I've tested LiFe Packs quite a bit now. 6,6V (discharge curve is pretty similar to a 5cell nimh pack), 3400mah, and the smooth/controlable 5cell feeling when driving.
It was great compared to lipo.
If someone would say 3400mah is not very much, I agree, but I used a 4t and a speedo set to max power and still was able to do 6 1/2 minutes of runtime, so you definately can do runtime.
That life packs last longer and are more secure is a fact.
The life packs I tested do have the same hardcase "efra lipos" do and are 10g lighter. So they fit any car and there's no balance issue.
http://shop.graupner.de/webuerp/servlet/AI?ARTN=98972
a link for those who want to have a look.
That's it for now.