You might want to take a look at the
"S.D.I." trimaran designed and built by Randy Reynolds. A smaller mainsail and a trapeze should allow it to be sailed into heavier winds as well.
I've come to notice a trend in trailerable multihull's mast-length compared to boat-length. It seems to be a "rule of thumb" for the mast to be 10' longer than the boat.
When building with metal, don't forget to add styrafoam blocks or other means of positive floatation in the amas and some areas of the main hull. Some people have used expanding closed-cell foam. If I were to go that route, I'd install a large, thick plastic bag into the hull and fill that with the expanding foam so it could be more easily removed later if desired, without having to scrape everything off the hull....