single 4s or.....

[kneedeeppow]

we have to run hardcase lipos here for events and 4s hardcase lipos are far to expensive for my budget so running 2 2s hc lipos is the next option(hobbyking 2s hardcase packs are cheap and seem to be good value for $)

[_paralyzed_]

hobbycity has a sweet 4s hardcase pack too

[_paralyzed_]

you're really close to the 15 minute mark already, so the extra 200mah might be enough.

You could also try a pinion with 1 or 2 less teeth. The lighter load might just give you the increase in runtime that you need. But of couirse check temperature often when changing gearing.

Good luck!!