Lipo questions

[Jbreddawg]

Ok, so I'm building my e-revo and have zero experiance with lipo's . I am "probably" going to go with 2 batts instead of one but have a few questions first. I was going to go with a 4s 5000 mah batt , can I use 2 2s with less mah for less weight ? Like 2 2s 2000 mah ? I know I wont get 35 min run times but will I still get the power output from them ? I dont mind 8-10 minute run times as thats about what I'm used to and will have 2 or 3 sets of batts . Am I on the right track ? Or way off ? I will be using a 9xl and an mm with a target speed of about 40 mph. Not sure on gearing yet but am using a monster rc motor mount with the revo tranny. any advice it appreiated !! Thanks, Jerry