Back in the mid 80's before they redid the tax laws and eliminated the General Partnerships, we planned to build a fleet of three cats. I believe they were around 56' and slept about 30 people.
They were designed by Dick Koogle (designer of the Witness Catamarans)of Ft Meyers, FL.
We believed they would be really solid boats and should sail at about 90% of wind speed, and planned on two very light weight diesels of mucho hp to get 15 knots under power.
The plan was to run trips to the Bahamas. Normal boats take two days to get to Nassau, while these could make it overnight.
Alas, the new tax laws made us lose our investors and the boats never made it past the drawing board.

But, we difinitely felt that aluminum would be far superior to glass (too much chance for damage on reefs, docks, etc.) I think steel would be too heavy and would really hurt the performance of a multihull. Multihulls really perform much better with lighter weights.

Good luck,
Rick