I ran about 2 gal cam 2 a few years back with about 3 gallons of existing tank (93oct). It's rated 114oct IIRC. This was the summer after I installed the S/C and I anticipated running it 1/4mile at a track north of here. Figures, I dump the fuel in when I am in the pits and then the skies open up for the rest of the day, closing the track.
Morale of the story - it wasn't meant to be and a greater power was warning me. 
I did run out the rest of the fuel, mostly on my ride home and revs were higher w/ snappier throttle response. That's about it really. Considering I wasn't on the track and it was raining, I didn't really get into it. But nothing beats the smell of burned off Cam. Just glad no po-po smelled it.
Gary Noonan
'01 S/C VX / '18 Forester XT