Done 2 Times
On Yamaha 21 footer and Speedster 150.
It is a great product, prevents much hull damage due to bumping trailer, hitting branches, beaching etc. it will yellow if left in the water full time, after about 5 years.
You cannot easily remove it, so apply carefully.
Prep is not hard but dont skimp on the steps. Hardest part is getting the strip straight as you lay it down.. wavy strip look awful from the front. They suggest two blue masking tape lines, I second that, measure carefully.
Get a small wooden roller to roll it in place after the initial tack down.
I find that tacking down about 2-3 feet at a time is the most you can do, lying under the trailer. If you make a goof, its pretty hard to un-tack and re-lay.
Length - 6 feet for Speedster 8 feet for Yamaha. Longer might interfere with water induction.