I have these
http://www.surfixinc.com/surfix_trailer_bunkslides.html on my trailer, the boat slides off almost like rollers, I can't undo the chain before the trailer is in the water, if I do she will end up on the ramp. The slides are soft so they will wear out in time, you have to make sure you change them before the bolt heads are exposed. I had them on my old Trophy for 4 years and they were still good, so it may take several years before they wear out. I use them on the rear bunks as well as the front .
You can buy them direct, they come in several different sizes , they are pre drilled and they will supply the S/S bolts .
I recommend you rip the carpet before you install them but they can be installed on the top of the carpet. They will not wear your gelcoat but you will notice it brighter more shiny where they are.
Here in AU we mostly use roller trailers but ever since I bought a US built bunk trailer with these I will never buy a roller trailer again, there is no need, with these you have the best of both worlds, good for the hull while on the road and easy to launch and retrieve.
I drive the boat on the trailer almost up to the winch post and I never put the rear wheels of the LC in the drink, when I launch she just slides off.