Oh and by the way, if you are consistently casting 70 feet from a boat
etc using small dry flies and turning them over accurately, then you
are well above average, and there is no reason why you should not be
able to use the gear described above. But if you take a couple of
lessons, and practice a little, you will be able to do what you want
to do easily and consistently.

In order to pick up, aerialise, and re-cast 70 feet of line in one
move, ( in the range #4 to #6 line and rods) you need a fast rod, and
the appropriate line. Nothing else will work. This is also exacerbated
by you sitting low down, you lose some height on the cast, but a long
rod will not compensate for that. Longer rods are only of advantage
if you can use them, or for specific purposes. Long casting is not one
of these purposes. Nine feet is about the maximum length most normally
built people can handle, even more so if it is a stiff rod. This is
because of the leverage. The added length will only allow you to cast
a little further if you can use the extra leverage, and most people can
´t. Not even many tournament casters, they stick to nine foot rods for
distance casting.

TL
MC