you are a nut job
in uk we have a small trimaran that one or two can sit in line in central hull , they are for disabled folk and their helper (if needed to sail) , they are pretty fast and give a great time to the sailors , but I bet given half a chance they would want to get out to the windward float and really power it up .
Ask my Fin Law he's 88 and sailing them.

If you insist on depowering your fine looking beast by sitting in the middle you best put a windscreen infront , the challenger trimarans I refer to are the wettest boats in the world to sail , with the spray from three bows meeting in the middle .which can kinda take the fun out a windy sail.

If you are building it in your "man shed " to do it justice , you should ditch the seats , at least tramp out to sponsons, and to be real "man " trapeze off them too , the design looks up to it .

full carbon construction too would be cool.

ps if you do build it with middle seats , do my fin law a favour and invite the ole fella out he would love it , even at 88 he still has the "balls" , but best not go into that , he's always wanted to put a big cat rig on his challenger .

good luck