I spent the last 6 years jumping from a formula board down to a 105 L bump and jump board. I would sail the formula, going down to my 8.5 sail at times, until I could easily plane on a 6.5 on the 105 L board.
I weigh 80 kg, so my experience will be a little different than yours. I decided that I wanted something to fill the gap (6.5 to 8.5 sail range) and decided on a new IS111, which I have been on 5 times, using my 7.5, 6.5 & 5.8. The 7.5 works really well with the board even though it is only 108 L. I haven't tried the 8.5 yet.
In your case, I would think the IS 144 is a bit too big, too close to the formula. The 133 is a better choice, but even the 122 can carry up to a 9.5 sail. The 122 may be a sinker for a 97kg fellow.
On the other hand, if you don't want to be on the formula very much and want the new board to work well in the lighter winds (12-15 knots), then the 144 may be your answer.
Hope this helps.