I changed mine from "AbCaRed.00" to current "AbCaRed00" [no dot] early on after problems with photo gallery access etc. [ fwiw: The photo gallery access did not work out so well with the '.00 user name [was unable to edit my first photo in the gallery with the original user name and was directed to another persons gallery ???].
Anyway, a site admin was also able to change over the previous posts made under the former name with the 'dot' to be ascribed to the new name so no old posts were lost and continuity was preserved.
Perhaps try an email to the 'admin' to see if they will still do this. It may take a day or two.
Just wanting to see if the forum will support embedding a YouTube video:
FYI: the first video clip was just pasted as the url link, and the second clip had the "s" removed to see if it would embed in the post- as it turns out, the forum automatically embedded both, so yes, the forum...