I got a set of these for my Viper's trailer. I put the old cradles on top of them once the boat is loaded. They make loading the boat easier than with the old cradles. They were more expensive than I wanted to pay, but they are nice and well built. I had them add the clear rollers. If someone finds a cheaper alternative I'd love to get a set for another boat.

Sharp looking boat by the way! What is it?

http://www.icarussportsusa.com/parts-and-accessories/double-rollers/