With out carpet they will rub the gelcoat off of your boat.

And the whole idea is to get away from carpet.

I just ordered the plastic covering and end pieces from Magictilt that goes over the existing 2X4s. Looking to see how it works out.

Try spraying your carpeted bunks with silicon. Your boat will slide right off, just don't unhook your winch prior to your boat being in the water. I treat mine a few times a year. Depending on how much you use your boat it lasts for a couple of months. I have the Gatorbak cover and they seem pretty good but are not slick. I spray them with silicon and they slip well also. I've had them going on 3 years now with no problem but worry the boards will rot, we'll see.

I don't have carpet

My little boat is way too hard to move on and off, so I am also looking for slick bunks.
Does not seem to be a good low budget option, except for using Trex, possibly.
Ultimate Bunk Boards are $192 for 2 x 6 x 12', not including shipping.
If gatorbaks, $210 for 12' of 2x6, are not slippery, then what is their advantage?
Delrin sheet of 12" x 12" x .75" is $104 at Interstate Plastics.
Amazon has HDPE 1"x48"x96" for $474.
3/4 x 6" nylon is $46.54/ft at US Plastic and 3/4" x 48" x 96" Polypropylene Sheet $307.29/sheet,
that's 8 8' strips x 6" for $307 + shipping- Hey, that might be OK, I'll split a sheet with you.
Its not UV resistant, but the boat sits on top usually.

If I were going to go that route, I would use King Starboard.. It's made for the marine industry and will not turn brittle oe discolor and is super slick. Cust pieces 6" long and the width of the bunk, space at aprox. 14-16" counter sink and attach with self tapping screws. You can probably do a set of bunks with no more than 1/2 sheet.

Interesting discussions going on over at the Basscat owners forum about this subject. Basscat has been researching alternatives for years. They recently went with Gatorbak but stopped using the product lately because of issues. I'm sure they are working out the problems but they went back to double carpet until everything tests out correctly. They are working to reduce the unwanted transfer of zebra muscles and other invasive species that can get caught in carpet.

Thanks Bob for the lead on marine grade HDPE.
Hurt myself yesterday loading my boat - it is light and should be easy.
I believe that 2 meters of the HDPE will expand over 50 deg C temperature rise 1.5 cm more than wood. That might cause a problem for long pieces screwed down into a wood base.
Might also be a good reason for short lengths with a gap, although some posts in this forum state a dislike for that arrangement.
US Plastics has 3/4" x 24" x 48" Polar White Seaboard� Sheet for $95

What about going back to roller bunks, with 2 compound rollers
http://www.etrailer.com/Boat-Trailer-Parts/Dutton-Lainson/DL21741.html

Tried silicone - did not work for me

Getting rid of carpet to reduce transfer of invasive species - great idea.

OP - If you don't like short sections of slicks, maybe you can drill slots instead of holes in the HDPE to reduce buckling/stress from the different rates of expansion?

Here you go. http://www.gatorbak.com/

Looks good but, and I don't want to sound ornery here,...
BigDad - see his 5/13/16 post - says the Gatorbaks are not slick.
G Rod said yesterday that Gatorbak is having some issues per the basscat forum.
Looking like the marine HDPE or the rollers might be the way to go from the current info.
Dawson, you started this discussion, what did you go with?

I called Gatorbak because I was curious and was told that their product provides more friction than carpet.

I have not got it done yet. Got a few irons in the fire. I like those rollers that got posted despite what I said. I'm thinking about uhmw as well. All the mentioned products can be ordered in appropriate sized strips to go on existing boards.

I have an 18ft SeaArk aluminum boat. The trailer has two 9ft 2x6 carpet covered bunks. I purchased the Surfix brand slicks and attached them over the carpet with countersunk stainless screws. The slicks work fine but after a year of trailering the with road vibration a couple of the screws started backing out. Now I am going to remove the slicks from the carpeted bunks and attach them to new 2x6 by through bolting with small stainless bolts and nyllock nuts. From this experience I do not recommend using screws to attach any type slicks, through bolt only!

I have ultimate bunk boards. I can't speak to the gel coat issue as I have an aluminum boat, but those things are slicker than snot when wet. Much easier to load compared to the carpeted bunks they replaced.