Here is a demonstration showing that it is possible to fit three long track snowmobiles into a 7x14 V nose trailer.
Inside dimensions of the trailer are roughly 80.5" wide X 196" long (To the V nose).
Snowmobiles used in the video are:
2016 Freeride 146
2019 Summit 154
2019 Summit 154 short tunnel
For this method to work, two of the three snowmobiles will need to have a narrow ski stance of 36" of less.
