OEM vs Viton Valve seals size difference

Greetings, 

I'm trying to resolve an oil leak in multiple cylinders that cause plug fouling in my 82 kz1000 k2.

It has a brand new set of Viton seals from Z1 in it that seem to leak.  I expected maybe I damaged the seals during installation.  I chose the cylinder that had the most oil in the intake runner and pulled the seal.   No apparent issue, everything looked normal. 

I happened to have a stock set of rubber seals that came with the gasket kit in addition to another set of Viton seals. 

When I place them side by side, the rubber seals have a visually smaller top opening than the Viton ones.   It mics out to about .013 of an inch (as accurately as you can mic a rubber seal opening).

So, it that normal? Should I consider the OEM ones? 
I hate to reassemble with the Viton seals and have the exact same issue.

Thoughts? 

Thanks
Scott

Do the Viton seals feel snug as they slide on the valve stem? If the stock seals have a tighter fit, thats what I would use.

The hole difference may be down to the elasticity of the rubber compared to the viton, as already mentioned how do the seals feel on the stem, also is it possible in replacing them you could have cracked a guide ? as a rule of thumb a leaking seal will present as significant smoke from the exhaust on "overrun" following hard acceleration (maximum vacum)

There is really not any difference that is noticeable when you get the seal on the valve.  It does exhibit the tell-tale blue smoke after a high rpm rev, in addition to greasing the intake runners and valves and fouling the plugs.

The guides seem in great shape, so I can't come up with any other reason for the oil in 3 of 4 cylinders.