Hi Neil
That is one of John Marples Fast Cruising designs. Looks like it is well built and would be a great choice for a modern cruising
trimaran. Like many newer designs they do give up some
interior accomadations for sailing performance. It will have the least
interior volume compared to a cat or
monohull tho in that size you should have plenty of room. It will perform better than a cat or
monohull and IMO for sheer sailing fun and pleasure you can't beat a
trimaran. Marples is in
Florida so his boats may not be as well known down under.
Some people have rational reasons for not liking multihulls, want more paypoad, don't care for the differant motion, don't like the non-traditional look, or a firm belief in the stability of the ballast
keel. That's okay we all have to be comfortable with our choices. Your brother on the other hand sounds like a 12 year old boy who swears he will have nothing to do with girls. Has he ever spent any time on a good cruising trimaran or cat? Maybe actually going out for a sail on one might open up his mind a bit.
With the more comfortable motion and better performance of a tri or cat your wife and
kids may even find that getting there is all part of the fun.
Good luck