Ok, Cheers
Does seem that they can be pushed a little higher than 1.35 then, I suppose without a DVM to actually measure the voltage We don't know how much over. Bottom Line as You found out is all these things seem to have sweet spots which are not at the Max and best for normal use
Same with every card, some are better overclockers than others.
I'll only ever use 1110 core for benchmarks and keep 1050 at 1.25v for day to day.
Hence the extra voltage of the asus card isn't needed even under water.
That doesn't mean that somebody won't get 1200 core with suitable cooling though.
My first 5850 was an appauling overclocker and wouldn't even go past 1000Mhz even with 1.35v.