Here's something I was going to put in the newsletter showing how simple it can be:
Sea-Lect Hatches
I was given a few hatch covers from Wilton Outdoor made by Sea-Lect for Valley rims. They sell the complete hatch and rims too and make them for Kayak Sport size hatches as well. They asked me to check them out and I have no affiliation.
I like them a lot. They are 100% water tight and snap on and off. They have a pull cord sheathed in a plastic tube for removal which allows them to pop right off with a little tug. They're convex and bow out a bit and are a hard plastic type of compound and laminated is an under-layer of softer material that travels to make the seal part. The large oval which fits the VCP oval has a little room around it so you don't have to push in the outer lip for a good seal yet they seal perfectly. At first they were a little stiff and tough to get on and off but now they loosened up and snap one easily and come off easy but still tougher than VCPs. I can't imagine one coming off under any sea condition. I gave them a shot of 303 in the beginning to help putting them on. They also have a notch for a tether. Since they're convex, you push down on them and they snap on.
The big question is: how much $ ? A few dollars less. They're supposed to outlast VCPs by far and they don't float. The Company is 6 years old so there really is no long-term tests on them however several manufacturers are now using them. The longevity of most products is based on the ingredients used to make it and the expected wear.
You can see them here:
The Connyak BBS