Just got the last club for my bag today.  Some observations specific to me, but the principles are common.

I have been looking for a club between my 910F-21 and 910 D2-10.5.  Both are Ilama by Titleist, the 21 is A-flex and the D2 is an R-flex.  I've tried a 910H-19 and a 910F-17 both in R-Flex (..on my own) without appreciable improvement.    The 910F-17 was fit indoors extrapolating from the available heads and shafts.  Got the 910H-19 based on the 910H-24/27 that work.  So guessing the club and shaft, even based on prior fittings, didn't work.  Along the way, there was a 19 degree hybrid in white.  Wasn't 14 yards longer, either.  Wasn't even as good as the 910H. 

Still had a gap between the 910F-21 and the driver.  Went for a fitting because the longer par 3's were out of reach of the 21F.  Went through 3 heads and a half-dozen shafts.  The 19 was short and the 17 was the obvious choice.  But it wasn't consistent.  The 15 wasn't getting enough loft.  The 15 was then set back to 16.5, and I hit the 21, 17, and 15 (16.5) while the fitter was down range marking the landings and roll-out.  The 15 set back is closed as opposed to the 17 that is .5 open.  The distance was the longest and the pattern tighter than the 17.  It is the first 3W I've been able to fit off the deck.  Couldn't have found that out in a booth

Fortunately, I have an Advanced Fitting Center in Madison - most carts only have 1 LH head in each series.  Like so many others that rave about getting fit outdoors - it is worth the effort to get done.  Travis is the patient fitter that worked hard to find something.