On my last post I explained how to set the pixels, just replace the <% = intAvatarWidth %> (both of them) with the pixels you want.
I can't tell you the line # on the file cuz mines have been highly modified but look for a line like this:
strTempMessageLink = Replace(strTempMessageLink, "[/IMG]", """>", 1, -1, 1)
and change it to something like this:
strTempMessageLink = Replace(strTempMessageLink, "[/IMG]", """ id='chkImg1' name='chkImg2'>", 1, -1, 1)
also add this line to functions_edit_post.asp on about line 67:
strMessage = Replace(strMessage, " id='chkImg1' name='chkImg2'", "", 1, -1, 1)
That should do it.