The problem might be getting the bearing off to put a shim behind ?, Hope not.
If the mainshaft was too big, It needed making smaller.
Some people use a chisel, Just to get it away from the wheel, I don't like that.
With the old brass cage you could get the puller to rest on the inner of the rollers, And pull the bearing off.
Wish you had an arrow to show the mark, Like Bruce does !, I can't do that !.
Do you mean the mark high up ?.
Also looks like something is rubbing on the screws ?, I hate that fitting.
As you say it looks like it will need a shim behind the drive side inner bearing
But you really need to see if the conrods are in the middle.
I wonder if you have a Big Pin Bigend, That sticks out more than the standard one,
I had this years ago, When I laid the Bike over to the left the Pin hit the C/C wall, Felt like the end of the world,
I was Racing at the time !!. People said I was a bit Slow, A, Richard !!.
When George Brown fitted me a Big Pin, Many years ago, He ground off both the bits of Pin that was sticking out, That's what I would do next time, But you have to do little at a time, With an angel grinder, So as not to over heat the Pin !!
Not sure you understand what Stu was saying, I think Stu ment , The Worm must be out wider than the step,
So that every thing is nipped up, See what other people say, It's a bit tricky.