That's all fairly reasonable. Not seen a 1/8 adjustable reamer yet but tempted with the 10mm.

What would be preferred though, interference fit or snug fit with grub screws?

And any more info on balancing with a scope?

My alu tube turns up soon so I can start building the spindle and once its done, ill get some pulleys.

I assume when turning shop bought pulleys its better to chuck up by the boss and not flanges?