This is the pair that I have currently on the bike. 7.5 x 2 = 15. 15 watts is reported to be the max output of the oem e50 (I said za50 above but I meant e50).
The bulb I linked to in the above post is 8.5w. 17w ought to be fine for the e50.. we'll see in the future. But the beam is rated (by the same company) at 90 lumens brighter, 10 degrees narrower, and 1000k whiter so it ought to be a noticeable improvement. As mentioned previously, Philips mounts these leds on a round heatsink-circuit board with all the circuitry they feel necessary to safeguard these bulbs against the range of crap low voltage ac that landscapers are liable to throw at them. Surely a 1984 howling vibration maker of a moped engine is at the bad end of that range.... nonetheless they've survive it just fine.
As to the original poster, YMMV of course, but these are grounded to frame with no negative effects for two pretty high mileage summers now.(edited)