The cheap alternative is:
* try using 7 or 8 cell AAA NiMh pack
* better yet, 7 or 8 cell 5/4 AAA NiMh pack
* You can also try 2/3 A cells, but it's a tight fit with the stock battery cover
* re-time your motor - this is quite a simple procedure, and it's almost like add an extra cell to your pack w/o the weight. I have a short how-to over at:
http://www.rcgroups.com/forums/showt...threadid=97414
Best combo I've been using so far for the EPS-300C (C gearing, on all the GWS planes) is a re-timed motor, 8 cell NiMh (5/4AAA or 2/3 A) and 9x7 prop.