Q about makita li-ion cells

[pinkpanda3310]

Recently I got a hold of some of these batteries. I won't use them for myself but thought I could make a pack to replace nimh's for someone else.

The cells are 3.6v, 1500ah, 10c (I think- at least that's what i worked to). So I made a 2s4p pack charged it up and gave it to this other person who ran it in a 1/10 truck (I think it was tamiya) which took 1x 7.2 nimh's.

Working to the specs I stated I thought it would be good for 60A and 6000ah. When I went to pick up the pack he said it was maybe 15% less power than his nimh's and only lasted 10 minutes. I took the pack home and checked the voltage, it still read 7.8v. So I figure the amp draw is too much for them.

Are these cells really not as goods as nimh's for rc or have I done something wrong??