Took advantage of a driver fitting last week. I took 3 varieties of my own drivers, 2 Wishons, 2 Tour Swing Xplodes, and 2 R9s with regular, firm and stiff various graphite shafts. I warmed up then hit each of them and the results were pretty much what I actually do on the golf course. Keep in mind I'll be 71 this year and normally use a regular flex shaft (UST/HOF/V2 etc) and a firm but never the stiff flex.
Fitter asked questions before we started and watched all my swings. Normally with a good swing hit a power fade,out of control a slice, when trying to over correct an over the top hook. Normally have a good controlled back swing, not too much turn with 2 herniated lower back disks and then normally too fast a downswing, tendency to sometimes come over the top, not following through completely making that turn for my stomach to face the target etc. I was told my swing speed prior to this with a driver was 88-90.
Fitter's first club out was the Callaway Rogue 10.5, regular flex and after a few changes with loft and shaft I didn't really improve and was really surprised.
Second up was the Ping 400 Max and I did better right off with accuracy and distance over the Callaway, but still too much of a fade and at times a slice.
Still not seeing sufficient improvement to spend that kind of money on a new driver (which I knew I couldn't afford anyway) so I suggested trying a Taylor Made M4. My playing partner who's in his late 40s and athletic bought one and his accuracy and distance improved over his Titleist. It was in stiff flex with the Atmos Red shaft at 10.5.

Fitter said they didn't have M4s as the M6s were in and they sent all the M3s and M4s back.
So I tried the $499 M6 and after a few adjustments was the better of the 3 but still not sufficient improvement to me. I don't have that kind of money anyway but wanted to take advantage of the 1 1/2 fitting session.
The Fitter then brought out another Taylor Made and told me not to look at it, just hit it.....WOW!!!
First two balls were nearly straight and 10-15 yards further than any of mine or the others I'd hit.

NEWS FLASH.....he had me hitting a TM6 D 10.5 set at 12.5 with a Tensei Orange STIFF shaft.

I couldn't believe it....never in my right mind would I have thought I'd be hitting a stiff shaft but boy it was the longest and straightest I've hit a driver in years. On top of that my swing speed was running 93-95. Now I am not fully educated on all the spin factors, loft, etc etc. But the Fitter said and showed me that the spin was coming down a bit on each change but once he went to the TM6 D set at 12.5* with that Tensei Orange shaft there were dramatic results......of course all I could tell was that the ball was going straighter and longer!
Just wish I could afford one ha ha ha!!
When I told my playing partner about it, it suggested I get a TM4 D and get that same shaft.

With me selling a few more golf items and several of the drivers I don't use I could afford the TM4 D version.
Anyone have any comments, suggestions or explanations on what I've written about above or had experience with the TM4 D???