I can see in the instructions that you want to have the inner side of the skate closer to the inner rail. I can see that the rails are spaced wider so
you can offset the wheels, what offset seems to work so that I can calculate wy rail width ?
Right now I have my rails only wide enough for the wheels to spin, about 2.25 on the inside.
The space between the rails is equal to the width of the wheel hub (with nuts etc.) plus 1/4 inch to allow offset. It's only necessary to offset the
front wheel by 1/4 inch (to the inside). Want more offset? Add more space and remember to center the rear wheel.