I think I touched on this in another thread, we had 2 NH 4.75 at the township. 12foot progressive mower. E540 worked ok in short grass thay was kept up with. Anything much over 6" (mower was set at 2.5" mowing height) you could forget about the e540.
The other NH t4.75 we flail mowed with. That 7 foot ferri mower worked in e540 some times. Anything thick or brushy you would have to stop and either drop a couple gears(normally mowed in 3rd range second gear, so would have to drop into mid 4th or 3rd) and or switch out of e540. Got to the point where I just left it in normal 540. Didn't see any fuel savings in e mode over regular.