You have two options:
The easy way is to simply install the freewheel on the six speed hub, and adjust the derailluer limit travel screw in the normal fashion to keep the chain on the small cog. You will have additional space between the small cog and the frame, but no functional differences except one less gear. I've done this when there wasn't a "proper" 6 speed freewheel handy, but it was temporary measure for me. Doesn't hurt anything, but why give up the extra cog?
The second option is to redish the rear wheel 6mm to the right, removing some spacers from the right end of the axle and switching them to the left side. The existing spacers on the axle may not work, and you may need to buy or fab up some replacements.
This way you should end up with a stronger rear wheel than either a conventional 5 or 6 speed wheel due to reduced dish. Phil Wood does something similar with 130 mm wheels, selling a rear freewheel hub for a 6 speed freewheel and a 130mm frame to obtain a stronger touring wheel.
Tom Adams, Shrewsbury NJ
Emanuel Lowi <email@example.com> wrote: Pardon this possibly stupid question, but I am not technically minded....
I have a 5-speed Regina freewheel I'd like to use on a frame spaced for 6 speed and on a rear hub also set up for 6 speed.
Whart do I do? Build the wheels differently? A simple adjustment of the rear derailleur? Or alter the hub somehow?