When I bought my '04 919 in November (my second, after the first was totalled by an inattentive driver in October), it had some scratching on the alternator/stator cover from a drop by the previous owner.
Forum member Tom very generously donated his old cover after installing the Circuit One cover on his own 919.

Thanks Tom!
I ordered the proper gasket from Service Honda; it wasn't very expensive, and apparently the clearance it provides is necessary as well. Don't just use RTV to seal the new cover.
I timed the alternator cover replacement to sync up with my oil change. I drained the oil, replaced the filter and then removed the 9 bolts holding the cover on. The stator is magnetic, and wants to stick to the flywheel, of course. So it took some tapping with my rawhide mallet to release the cover. There wasn't much oil loss, since I'd already drained the oil, but I kept a pan underneath to catch the drips nonetheless.
After removing the cover
Old cover containing stator
I elected not to unplug the 3p connector which would release the stator wire, so I had to keep the whole arrangement balanced on my knees.
I scraped off the old gasket material, then applied a very light coat of RTV to several spots on the mating surface, and attached and aligned the new gasket. I removed and cleaned the 2 dowel pins, long and short, and unbolted the wire clamp and the 4 allen bolts holding in the stator, then bolted everything back into the new cover and replaced the dowel pins.
With new gasket
Closeup of reduction gear--long dowel pin on the cover slides in here to become the reduction gear shaft.
Closeup of wire grommet seated in new cover (I used a bit of RTV to seal it in)
Realigning the new cover, the bolt holes, and slotting the dowel pins into their holes was challenging.
The magnet wanted to pull the cover and stator on, but seemed to want it to be misaligned. It took some frustrating fiddling and moving the reduction gear onto the long dowel pin before I was able to align everything--but at last, victory was mine. I made sure the wire grommet was in its proper place, then torqued down the cover bolts.
All buttoned back up, no scratches!
I then added the oil, and was ready to ride.