RE: is there a Q500 construction thread?
Thats really too heavy. A couple decent batteries worth looking at are standard 270 or 350 mah NICD's.
If you comfortable with NIMH's you can go with 500 mah or 720 mah batteries.
Just make sure you charge/discharge them a couple times and know where they are at, and what they are capable of. These batteries are under 2 oz, and really where you need to be to get to a decent weight.