First let me say how happy I am that CVKs had the hatch cover, given the issues with supply lines.

Re the hatch cover, it fits tight, very very tight. It was very difficult getting it on the first time and I'm hoping it will relax with use. The trick to getting it on the hatch of my 10 year old Valley Aquanaut was to start at one end and make sure that the edge on the inside of the cover was fully inserted in the slot that goes around the edge of the hatch, then move gradually to the other end of the hatch making sure it engages all the way along. I found a small piece of 1/4" plywood was very helpful in pushing the seal into place as I went along, as were well placed hits of the reluctant sections of the edge with my fist. This was when it was 26C out. I don't know how well the technique would work if it was colder.