Lots more than 10 cents worth of info there. Any idea how thick the spacer would need to be to counter any offset when using the GW rim?But to go darkside properly on a Valk will require switching to a 16" goldwing rim just to get a choice of tire sizes. It's doable if you have a spacer made to accomodate the GW rim. After that it's just trial and error to find the best performing tire size for the bike.
That's just my .10 cents worth.