Sorry guys but the SZ is capable of mowing at full stick. Just need the right conditions, ie short dry grass and a smooth surface. That said, the grass I cut is pretty dense like bermuda so not really worried about vacuum etc.
It isn't a matter of suction/vacume mate. It is the fact that there simply aren't enough blade strikes per forward inch of travel to cut cleanly at that speed (much less than one side of the blade striking the grass, or less than one strike per forward inch of travel). I'm sure on some of that stuff you cut that is fairly stiff, it will do a fair to good job, but on many of the grass types we have here, especially in the northern half of this country, it simply won't leave the QOC that many of us need at that speed. There'd just be too many stragglers left behind.