From what I can see, the F100 flies a very slow cruise (220KIAS or less) then into 250kts or more on descent
I don't think the issue the speed the F100 flys at, but rather the shorter sectors they fly. It's hard to loose 20 mins on an hour sector, but the F100 is probably the aircraft best to give it a crack.
For me personally, I find it easier and more accurate to cruise at the slower speeds and have the extra power in reserve for increasing to meet the times. There is only so slow you can go (even in the 100
) if you've come in fast and need to slow down. And as already mentioned, that is probably the crux of the problem. Too many people skinning the same cat in differant ways.