If it is the TT that had huge tail cut-outs, it needs a fin that is near vertical in rake, it liked to sail very flat.
The F159 was a lot less fin specific and went really well with most fins. For just messing about on as a light wind board, it will even take a 60cm fin to help increase top-end and gybing.
Out of the two, the F159 is the easiest to sail down wind (and I felt it was fast too). Fanatics 2004 and 2005 TT's were nice, but a lot of formula racers were not happy with the TT 06, the 06 was the last formula that Fanatic made. Fanatic say it was due too the PWA replacing formula with slalom42, they said they wanted to develope their slalom range instead.
The F159 was a great board in its day and is definetly better suited (now a days) for a fast light wind machine. Grab the F159 before it goes