Just got thre folloowing email back from the battery people...
Hello
Yes 4 amps will be ok, we do 7.2v 2400mah as packs made up, we also have 2400 AA with tags.
All the 2700 we do are normal AA type with no tags, you can fit two packs in parallel but it might be better to charger each pack up separately before use.
Thanks Paul
Working on the fact that two packs of 7.2v AA are about the same weight as 4 "C" cells for anything running motors drawing less than 8 amps you will end up with a light weight 4.8ah cell Pack...
Sounds like it might just work, I'll keep you posted.