if there is a 3/16 plate welded in that is already a sign that the frame has been repaired there.
I don't know why the 2 whl brkt won't work, but no one stipulates that it does work.
i made my own brkt
ron

http://s908.beta.photobucket.com/user/padresag/library/turned%20works
http://s908.beta.photobucket.com/user/padresag/library/furniture
and a little history of where I come from
http://forum.woodenboat.com/showthread.php?156542-old-boatshop-in-Steveston