ok, i don't take that risk and go for 11.0+, like you said thats how the parts are together...always fun to hear what you/people on fabo have to say about this things.
thats about the max on a stock stroke 340 with what i consider a mild solid roller,but you cant have a bad batch of fuel and make sure you stay out of the throttle if you dont have plenty of cool down time after a long time of building heat during a cruise night :) on swedish V-Power that is.
back to topic they are pretty good heads for what they are, just make sure to have the guides and seats checked if they are new