fred,
The pictures while looking at them while in the hospital I could not tell if that was a shallow draft keel with a swing center board in the shallow draft keel or just a swing keel only. If it is a shoal draft keel with a centerboard inside the shoal draft, then launching and retrieving will cause the trailer to go back farther as it sits higher on the trailer. A long extension will be needed.
There are a few things to consider. First I cannot tell what the deminsions of the winch stand/bow roller is but what ever there should be a forward support angled to reinforce that stand. I have not seen a photo of the attached winch stand which you said that would be send.
Secondly, you should have either a 2 X 4 or 2X6 treated lumber with carpeting attached to the upward supports laying flat on the hull so they can be curved. If that board the way it is attached now on its side should break my friend, the hull will be peireced by that support. I also suggest that you also add bracing to the four supports for added safety.