Countersinking and through bolting is a good method. The trailer that came with my Seaark the bunks appear to be attached with through bolts, at least the side guides are because I have already lost a nut and washer off of one of them. I have the covering for the bunks ordered from Magictilt and they should be here today. They are the kind that covers the 2X4s. I'm going to use #10 screws and washers to attach the covering but I'm going to replace the existing nuts with new ny-locks and put lock washers under them. It's kind of a belt and suspenders approach but I'm doing the work and it's only time.

The trailer that came with my 18ft Seaark has two 10.5' bunks that hit on each side of the keel and support the entire length of the bot and two 6' bunks that support the outer area.

My bunk material from Magiclift just arrived and it looks pretty good, slicker than the bunk carpet I have. It comes in lengths of flat material that bends to form around the 2X4s and fastens with screws. I think it's going to do what I need it to do.

The Surfix slicks look good, may be the top commercial product so far (ignoring the roller bunks). How slick are the ultimate bunk boards when dry? - like when unloading the boat?

They look good until you break out the calculator and figure the price for square foot, then not so good. They are charging a lot of money to cut, radius the edges, and countersink for the screws. You would do a lot better with Starboard and the stuff is very easy to work with standard wood working tools and basic woodworking skills. But then, I'm a DIY guy many people are not.

They are pretty slick when dry too. The boat comes right off. I would not ever try to back the boat down the ramp unhooked...

I don't even do that with carpeted bunks. You just never know.

The MagicLift looks like good material and easy to install, similar to carpet.

Prices I have found for alternate bunk material:
Surfix Board, one board 5" x 54" =$30 ...per linear foot (5� wide) = $6.67 1/2� thick
Ultimate Bunk Board 2 boards 2x6 x 6' costs $96 ...per linear foot (6�wide) = $8 2� thick
US Plastics 3/4" x 24" x 48" White Seaboard Sheet =$95 ...per linear foot (6�wide) =$6 3/4� thick
Deluxe Roller Bunk � 2 x5'- 12 Sets/2 Rollers $104 (options) ...per linear ft = $10.40
Magiclift � could not find a price
Cost of new structural pieces? Time to install?
One version of roller bunk will simply sit on top of my bunk � easy installation
Ultimate Bunk Board,Surfix and Seaboard are all HDPE with UV resistance � the same stuff

You also have to keep in mind that any of the thick material that attaches to the existing bunk board will require the trailer to be a little deeper in the water to launch and load. Also, depending on how close the bow eye is to the roller, you may have to raise the position of the winch.

If the stuff from Magictilt doesn't pan out, my next choice will be to cut blocks of Starboard and space them on the bunks, since I can buy the stuff at wholesale. The disadvantage, and the only one, to Starboard is that if you have to have it shipped, it will kill you, the stuff is really heavy.

I have been looking for bunk brackets that will sit lower so I can keep the boat height the same.
Since I already am at the minimum height with my current brackets, I may have to weld brackets onto the frame.
At this point I am planning to go with 3/4" Seaboard from US Plastics over a 2x4 on its side. That should be a very slick setup for the 16'. My back will be thankful. Expensive, but so is a bad back.

Have you got their web site I can't find anything but bras

Here is what I use. I've had them on for about 6 yrs now and they work great.

http://www.iboats.com/Tie-Down-Engineering-Bunk-Glide-Ons/dm/view_id.40440