The squareroot of the waterline X1.34 applies to most hulls including multihulls. However if the hull width is narrow then a higher speed can be achieved, before the resistance produces a bow wave.
If the hull/hulls have a length to width ratio of 16 -1 "the displacement
rule" does not apply and these boats do not form a bow wave even at high speed (30 knots) (Commercial ferries) The difficulty is that it is difficult to design a practical boat under 200 ft using this principle.
I have also found that by designing a hull in the shape of a wedge with a very narrow angle of entry and a wide stern I can also "Break" the displacement rule
and achieve high speed without forming a bow wave.
I am building a 40 ft Power trimaran
based on this principle which is powered by two 30 hp Honda
outboards and will be able to cruise
at 20 knots. I will be in the water
in about 4 weeks.