On your diagram use the track labeled "unused T track" just get a sliding ring that you can attach a ratchet block to and you are done. Ideally you would install a padeye in the correct position which on a trimaran
can be tricky. Monohulls are almost never quite as wide as you would want them, a tri can be a little too wide so the typical advice of as far back and outboard
as possible doesn't quite work. The exact location depends on the sail, the boat, and the angle of the breeze. For now just use the T track and don't stress over it.
Attaching something lower has the same effect as moving it forward, so there isn't much to be gained here by doing that.
I wanted the rig dimensions to do the following...
I - Deck
to mast head
J - Mast
to bow - 12'
So the luff length of your jib
is SqrRoot ( 43^2+12^2) = 44.6'
If you add a 5' pole it is 46.24
Now go to North Sails
Direct for their prepackaged chutes. With those luff dimensions you are looking at....
44.6 - model 42
46.24 - model 46
These are a little larger than what I had assumed. I would also recommend pricing out a tri radial from other lofts. North Direct has pretty good prices, but others lofts are also doing prepackaged sails
any may have a better cut for you.