A few notes -
When you get the threaded tapered shafts make sure they will run true. I rarely bother to send things back, but the first pair I got had a serious wobble. They should run with virtually no detectable wobble.
A motor speed of 3450rpm - probably what you have - is good. The surface speed of the buff, especially with tripoli, will make a 5" to 6" diameter buff close to optimum. It's a continuum, so a 4" buff will work, just won't cut as fast.
For exhaust, I have a box with a large squirrel cage blower - say an average house furnace size - and it blows through a furnace filter and recycles the air. If you have a warm climate and the chance to exhaust outside, that's better, the less restriction the better. Only if you work with gold is collecting the residue important.
I used to have both spindles mounted - tripoli and rouge buffs -but elected to just use one for any buff so I could have a more direct suction from one place.
Mine is wide open, no cover, the suction is enough that little escapes. I've never used anything with a cover but I'd think it would quickly get enough dust and gunk on it you wouldn't be able to see properly And you really will want enough range of hand movement to hold the piece being buffed in many orientations and even body positions.
Oh, never be tempted to wear gloves, I usually use folded paper towels to hold things, keeps the heat from the fingers and will tear easily enough.
And never be tempted to polish chain on it.
So much more I can't think of right now....
