John,
I have had a unit for a while.
I found the cloth backed 100mm sanding material works well. It is easier to purchase and cheaper than the 75mm and saves you cutting the 100mm down to 75 as 100mm was all I could get in long rolls of fine grade. It is a simple matter to generate a template and cut out the sheets. I generally only use the machine for finish sanding with fine (~120 grit and finer) 'paper'.
I like the idea of opening up the dust intake to 100mm as suggested by another post.
The tracking is fiddly at first but once set is ok.
Make sure the sanding material is tight on the drum, or it will wrinkle, and only do light passes.
good luck
.........peter