5 short tracks and a 136 should be no problem. You have to mix the sleds forward and back. Were two sleds are in forward, throw the rear of both sleds all the way to the sides and then back another up in between them.
We have put 5 151-162 moutain sleds in a 28 footer several times. I use to haul 2 121's and a 136 in my 14ft all the time. Eric