If you were fit for the Diamana shaft then why are you considering the Fujikura shaft? Maybe you should take both shafts and go see your fitter again to see what recommendation he/she gives you after hitting with both shafts.

with that swing speed I would go for a lighter shaft. The more energy you can get into the ball the longer and better ball speed you will receive

With all due respect, none of us here would tell you which shaft to use. If you didn’t believe the fitter, get a second fitting. You can get it free using the Titleist Thursday scheduler. Too many variables. The TrackMan data and hitting at a range should give you the best information. Nothing more personal than the club fitting experience.

This

It would unfortunately be a guess at best without any LM numbers to compare the 2.

If you happen to live in a spot where you don't have access to Trackman/GCQuad (we don't have those here to use). So if getting on a LM is not possible then maybe use 1 on the front 9 the other on the back, or some good range sessions to compare the two (again if only not able to use a LM to figure for sure what fits better)

I agree with all of you and I have every confidence in my fitter.
It's just that I've just bought the D2 and and it came with the Fujikura already fitted
and as it was a regular flex I thought I would try it out. I'm not to bothered about it as I know the Diamana has been fitted for me in the D3 so I can use it in the D2. My thought process was that as the D2 has a slightly higher launch angle than the D3 so would the Fujikura help to keep it down a bit !.