Since the bike shock is out of the picture and I am building a custom motor mount...
I guess I am making a swing-arm too.
I like the tube look of the magnum swing-arm so I want to keep that look. I will add to it and take a page from Ducati and incorporate a trellis into the swingarm to make sure it is nice and strong.
The main part of the swing-arm will be made out of 1 1/4" .120 wall tube and the lower part of the swing-arm will be made of 3/4" .120 tube. I wanted to make sure it was strong but not make it look bulky. The swing-arm will be mounted through bearings so make it solid and pivot smooth. The trellis section will angle off the swing-arm mounts and meet the other angle of the trellis at the mount for the shock. This will create a nice strong triangle and I will build in a few more smaller triangles as well.
I will be building motorcycle type chain adjusters and having them welded to the tube swing-arm. These will allow me to use a through type axle that is not actually attached to the wheel. Since I will be using sealed bearings on the axle this will work out fine.
I need to finish the motor mount and get it welded to the frame before I can start work on the swing-arm. Most of the measurements on the swing-arm will be derived after the motor mount is set.