I ran two Maxamps receiver packs that I rewired in parallel. They were the 1290mah 2S3P packs. Maxamps might be willing to assemble them all in parallel as a saddle pack if you ask.

I'm going to rewire mine to be a 2 cell pack so that will give me almost 2600mAh. I'll have to gear accordingly and roll it to make time but it should be a rocket on the straight.