This thread hasn't been visited in a few years. I recently found the following information on the Internet in regards to Welch Island.
http://www.bluewaterrealtygroup.net/...Winnipesaukee/
As a teenager spending Summers in the 50's and 60's at Lake Shore Park in Gilford, we use to have an "Iron Man" test, which was to swim to Welch Island and back to LSP. Of course we were accompanied by a boat.