Ideally it could do with a skim, but if going anywhere near a machine shop, would be money VERY well spent having it lightened, they are seriously heavy, my own one went from 8.9KG(std 2wd sapph) to 6.6KG after lightening, now being slotted, estimate down to 4.8-5.2KG.
A normal skim, lighten, balance should cost around £50, unless you're running a paddle clutch most blue spotting which is normal doesn't cause a issue, mine have been blue the complete width and circumference and didn't give any issues.
tabetha