I am assuming you are flying with a stock Hummingbird motor and Birdseed pack. With that presumption, here is what I have to say.
I think you are approaching the problem the wrong way. Instead of trying to modify the heli around your battery pack, you should be modifying the battery pack first.
If you want to fly longer it's the battery pack itself you must change. Throw that Birdseed pack away and get some 1200 E-techs li-poly batteries and you'll double, possible triple your flying time per battery pack and because the Li-polys are so much lighter you'll get a better climb rate as well.
Oh, and getting a better motor will certainly help as well.
I notice this is your first post, perhaps you should do some searching and reading in this forum. Lots of good info in here on how to get better performance out of you little heli.