OK, so i am new to the inline trailers with my Neo 3 place....18' box,+ 5' nose. I currently have a 136 and 2-121's in it. Because the sleds are staggered and the extra length is always to the back of any sled, I'd say that 3 longtracks would fit.
On one side I have the 136 and 121 inline and there is 32" betweem the snow flap of one and the front bumper of the other with plenty of room on the other side with the single 121.