Well, this is a work in progress, but attached you will find a worksheet that you can use to fill in the blanks and then go to work. There are some people who have already used this guide to do installs (including me) and it works well. For those people who have already installed skids in their RX-1, I would like you to populate this thread with posts having the dimensions for an SC-10 III skid, SC4, Thundercat FasTrack, etc. For my case, a Polaris Pro-X 136" skid had the following dimensions: Y1 = 6.5" Y2 = 5.375" Y3 = 5.3125" X1 = 9.5" L1 = 27.25" Y3 can be at the discretion of the individual, depending on what rear height you are looking for. Generally, you want to use exactly as was on the donor sled. Any questions? Just post.