Any extra AD, be it runes or items, will not add any damage to it, and yes, I suppose it would be 1.8 times base damage times 2. I'm not sure which is taken into account first, but I think it's Sheen. Again, if you want to continue with this idea, Trinity Force, man.

Wow did I misread that one... so that means that each Sheen activation will only add about 96 damage to any given hit (not terrible I guess)... hmmm... maybe I should try an AP build with Lich Bane then... Thanks for the help, much appreciated... I'll let you know how new testing goes...

... does increased attack damage in runes add toward base damage, or is it just tacked on after?

... also, if I crit a Sheen Boosted attack will that attack's damage be my base damage times 1.8, and then all that times 2?

I just thought I'd point out that Sheen increases your BASE damage, not your total damage. His ult won't increase the extra damage, nor will any AD items. You could go for Lich Bane and get more AP. Lich Bane increases the next basic attack by 100% of your AP. Also, be aware that the Sheen boost has a 3 second cooldown. If you'd like to continue with this idea, (and it could be a good idea) I'd upgrade Sheen to Trinity Force. The bonus will be 130% instead of 80% and there is no cooldown.