If I owned a Trifoiler, the very first thing I would do with it would be to cut a hole in the bottom, and add a mirage drive well in the cockpit. Plenty of retrofits have been done on sit inside kayaks, where they just build up 4 walls on the outside of the well (so water doesn't fill the hull), then snap the mirage drive in there. When not using the Mirage drive, the box can be covered with a lid.. It would solve all the Trifoilers problems with getting out of the harbors, and getting around when the wind dies, and it's upwind difficulties.
Once the hull is out of the water (on foils), there is no drag penalty, just park the fins against the underside of the hull.
Once this is done, then it's a very simple matter to just add an Evolve system, just plug it in to the mirage drive pocket. Again once your up on the foils, the evolve system is completely out of the water. Adding 15 lbs weight into the mix is not going to be a show stopper on a 350 lb boat.
The way I figure it, if I had ten grand to spend on a Trifoiler, I could easily come up with another $2500 to add an evolve system with dual batteries, and a couple optional solar panels. The panels would be rigged behind the spars (plenty of room for them).
Another less expensive option would be to hang a Honda 2.3 motor on the Trifoiler (Dan Ketterman had I think a 5hp on his for a while).
I have a Honda 2.3 on my TI, and boy what a difference it makes. When the wind is not cooperating, I just fire the motor up and powersail. I can go out all day powersailing for about a dollar or two in gas.
Of course once you get far enough offshore so you can foil, you just shut the motor off. Again adding 30 lbs into the mix is not going to be a show stopper on a 350 lb trifoiler. I've seen several videos of Trifoilers out with 2-3 people on board so adding the motor, or Mirage drive/Evolve system would be a no brainer for me.
Actually I would probably do both.
The second thing I would do is get rid of the old 15-20 yr old sail design and update the Trifoiler with more modern wing sails like the latest moths and the windsurfers have. With wing sails you would open up the boats capabilities beyond even what I can imagine. Things like foiling upwind at 2x windspeed, and downwind 3x windspeed would be easily accomplished (just like the AC 72's). Now I'm not talking about the big solid jointed wings like on the AC 72's, when anyone mentions wing sails, that is what everyone pictures in their minds and wants nothing to do with them. I'm talking about double walled semi rigid sails that from a distance look no different from standard sails, the jibs on the AC 72's are this type, and that type of sail is what I have on my TI, and boy what a difference it makes, they work completely different from normal sails, so you have to throw away all your old books and learn a different way of sailing.
With the above mentioned system, I pretty sure I could get into the high 40's on a regular basis, and in a lot more conditions. I'm thinking your speed limit would be when the foils begin to cavitate, or you start getting scared (whichever comes first).
The Trifoiler design like I've said before was 15-20 yrs ahead of it's time, but even to todays standards, the foil system is one of the best out there thanks to Greg Kettermans genious. But keep in mind this was a long time ago, and the world has progressed quite a bit. The Trifoiler started out as a High school project and was designed around current 'for the time' knowledge. If he had thought up the Mirage drive first, I'm sure it would have been incorporated into the mix, but that didn't come till much later.
I just wish I had one so I could soup it up, but that's never going to happen, I just don't have that kind of money to play around with.