Hello PUCHOCOMETA
I just finished my little MiniMax yesterday. Mine came with a 320 Ma pack. Ihaven't used that pack yet . I am using a Qualcom pack and bypassing the circut board on the pack. It has good power and will take off at 1/2 throttle indoors no wind.

I got it to loop and and will try to do some inverted flight tomorro.
The 280 seems to have power to spare with these packs. You can get them here. http://www.hackettelec.com/~hackelec/qc.html

And you have to modify them look here
http://home.attbi.com/~zagizagi/lithium/
or here
http://pease1.sr.unh.edu/aew/rc/HowTo/Qualcomm/
or here
http://www-personal.umich.edu/~aroge.../qbattery1.htm

I don't have any connection with any of these sites but used their ideas. Good luck John