Here is my trainer used as a glider tug. It is almost 10 pounds in the video.
http://www.youtube.com/watch?v=V5k-h-n5IVA
My setup is a Monster power 60, Exceed 60 amp esc, and a 6s 5000mah battery. I am using a 16X8 APC "E" prop. I could go a little bigger on the prop, but this is a good mix of power and duration. I get almost 30 minutes of flight time when I am just cruising around.
Buzz.