Pete the margins are their for all aircraft the thing is with a speed tape or indeed a MASI you are constantly reminded where they are. The upper maneuvor margin of 0.3g is/may be displayed below the Mmo/Vmo, red and black bricks if you prefer, at high altitude at reletivly high gross weights on the 73NG, just where you would expect. Straight a level flight poses no problems, if you realy want you can still fly into the upper maneuvor margin up to Mmo, what you of course must understand is that any loads whilst in this region, maneuvor or gust may induce high speed buffet, thre bottom of the bar providing 0.3g. The B73 however displays excelent high speed stability with little or no tendency to tuck.
Best rgds