Studding Question

I have a 2004 rev 800x with a 121 inch track. How many studs will I need if I use a pattern with 4 on the first lug and 3 on the next and continue this pattern untill finished. My sled currenty has 120 3 and 2 pattern in it and I want to add more studs using a double backer on the track rungs that currenty have 2 studs in them now. This will give me the 4 and 3 pattern noted above.