I have found that the skids go in easiest for me if I do the following:
1. make sure rear wheels are as far forward as possible
2. raise rear of sled off ground to give full access to the track
3. slide skid into track front first
4. use ratchet straps on each side of sled to pull skid toward rear
5. bolt in front brackets
6. Insert bolts for rear bracket
7. tighten track by moving rear wheels to rear of skid
7. lower rear of sled
8. take for a ride
Taking this approach I had the skid out, serviced cross-shafts, and back into the Invader in less than an hour.