I had the chance to get out in the mountains a few days ago to test out some mods and things on the Z. Here's what I came back with.
Castrol Power RS Racing 4T 10/40 full synthetic oil: No usage, no leakage, no color change in 50 miles. Runs smoother, quieter, a bit cooler on average. Transmission shifts through the selection easier then with conventional oil and throttle response does feel a bit quicker..oddly. But the most important part was that the wet clutch had no additional slippage. In fact, it had less. I even purposely stopped it against several downed trees and rocks in high range-2wd and pushed it to go over them. No additional force was needed, no issue, no problem. So, for this short of a test I would say it's not only safe, but good for the engine. I don't see any reason not to use it. Just make sure yours is well broke in first.
UPDATE 5/19/16: On a ride we had together on this date
Jogon30 reminded me that he has been using this oil for some time now with very good results.
Throttle Peddle Modification: This is where the lower part of the arm was adjusted to allow it to tip down farther and the arm's return spring was adjusted to increase resistance. This mod completely eliminated my foot and leg fatigue making the ride much more enjoyable making it a must-do IMO.
Benz Silent rider (silencer): From the cab position this pretty much eliminated the exhaust noise and was a welcome addition. The setup didn't seem to have caused any loss of power.. however it did allow the noisy drive train to really stand out. Boy are these things noisy! The only thing I need to address is that one of the rubber/plastic parts on the moto just above the silencer isn't protected by the heat shield and needs one. Although it didn't burn or melt, it was hotter then I want it to be.
1.5" Wheel Spacers: These seem to help with off-camber situations some but had no noticeable ill effects on handling or steering performance. I see no reason at this time to remove them.
10.1" tablet used as a GPS: In the desert or lots of sun this proved to be near useless to me but I thought I would try it in the shadows of the mountain woods before tossing the idea out the window. In the trees it was useable and nice to have. I use satellite or aerial maps so I can see what's coming and zoom-out to see where about's on the mountain I was. So, I'll use it in the woods and my Garmin in the desert for now.