Noel,
I have set it to the low speed for the 3″ wheel I intend to use which has a speed rating on it.
I have also made an 1/8″ thick aluminium guard for the drive belt and a steel semi-circular guard to surround the wheel as much as is feasible.
I would like to keep my sight so will be going very carefully when I use it.
I am just sorting out suds as well. I have a friend who has used these devices at work and will have him here for advice when first use it.
Colin