Black deposits on pistons

So I have everything back together and I'm just about to put the head back on.
I got myself a vesrah complete gasket Kit. Which has been great- except for the fact that it doesn't include the 4 o rings for the stud oil passages (which I don't understand- it has everything else.)
I did wind up have the seats cut by Larry Cabanaugh. Just had a baby- so I didn't have time to work on the bike anyway. Figured it was best to do it while I had everything opened up.

I do have one question though. In the complete best aj gasket kit- it comes with a two piece head gasket kit. The gasket has the metal circles inside the grey fibre.
My question is: what side goes up?
One side of the metal looks like it is been machines flat. The other side looks like the inside corner has been tooled over towards the center of the piston.
The z1 site suggests that the metal side with the wider exposed metal faces up. Problem is- both side of exposed metal are within a couple hundredths of an inch of each other...
What side is up and what side is down?

Larry also refaced all of the valves and relapsed them while he had everything in his shop.

I have to admit- the viton rubber that comes with the billet end plugs is difficult to deal with.
Hearing the stories about using the rubber- and still having leaks (there is a joke here- but I'm keeping the post PG rated..) I decided I would take a two stage approach. I wanted to use the viton rubber and a sealant (permatex ultra copper).

But keeping the rubber I place and applying the sealant over the top, and then seating the part inside the head was, to say the least- problematic. So the super glue was used to tack the rubber to the end cap. Then the sealant was applied over top the rubber inserts. The cam cover was then torqued down over the engine to push everything down and will sit over night.

I'll finish everything tomorrow and report how the dual method worked out!