This is the Viking 6" access hatch; actual opening is 5.25". It was about $25 at Pacific Water Sports in Tacoma. Included is a detachable nylon (coated?) bag that is about 12" diameter at the bottom, which does reach to the bottom of the boat. I cut a circular piece of .5" foam to fit that to help keep the bag "open".

During construction, I knew I'd be installing this as well as a rear deck hatch, so I simply 'glassed (6 oz.) the underside of the deck for about 3' aft of the cockpit. The cutout nipped about a 1" x 3" arc out of the rear cockpit reinforcement piece, but with the bulkhead right there and the extra 'glass, it seems to withstand my flopping around on the deck so far. The low profile doesn't snag or interfere, either.

Using the lid without the bag, have your wife sit in the boat and experiment with final placement. You can hold the rim while she reaches behind and tries to unscrew and replace the lid. This may take some practice, even with the boat sitting on the nice, stable lawn. And it's even trickier out on the water.

Since the deck panels on the Coho are flat, installation is pretty straightforward. Once you have the location, cut the proper-sized hole just like a hatch. I made up a rubber gasket to fit between the mounting plate and the deck. The mounting screws were either #12 or #14 x .75" long stainless oval- or panheads. After initial mounting, I removed each screw and ground off the excess length. Epoxy seal the big cutout and the screw holes, and reinstall everything.

Rig a tether to the lid!

I like it. My first iteration was a similar screwtop-and-bag that I installed in my nylon fabric sprayskirt, but that wouldn't be waterproof in a wet exit. I can't remember when, but some time ago there was a letter-to-the-editor in Sea Kayaker denouncing the deck-mounted day hatch. I think it was a warning that while the hatch is open, you have a hole in your boat.