dont machine the melonite surfacing off the whole plate, just take the tops off those sharp knots. it will likely be a bit of a hassle to build yourself a jig to hold the plate in order to machine the plate. its probably alot easier to use a small grinder of some sort.
when i first ran into those, i have a 2" right angle grinder that i run a 80grit pad on. i would shave the tops off those knots and then put on a red scotchbrite pad on the 2" die grinder and polish the plate out. you can use some of the buffing pads, the red or green on a small die grinder and polish that plate to a mirror. the hardened melonite coating wont grind off using one of those buffing pads. it will polish the surface smooth like glass. the smoother you get that plate, the smoother and more responsive the clutch will react. the least amount of friction you can have, the better your setup will run. the sliders on the plate, and 6 pucks that the weights sit in is a carbon and graphite composite. they lubricate themselves and slide with ease. but having those sharp edges portruding on the plate is causing alot more friction in the whole system and keeping your clutch from operating like it should.