Hi Ed,
Wish I had more carefully documented fuel burn vs airspeed on the -B drive & old prop.  But from the few well documented points that I have, it looks about the same at 6.0 GPH (sea level) IAS, 143 - 148 depending on OAT, humidity, etc (its amazing how much conditions affect things).  This is the only point I've had a chance to compare so far.  I have not built the prop blade cuffs that I feel will be necessary to get best performance from this combination.  Clark at Performance Props was very honest about the difficulty in getting the proper pitch at the blade root (out to ~ 3" past the 13" dia. spinner) with pitch this high.  This being the case, I'm very happy with the results so far.  Other conclusions are that anything less than 74" L prop is a waste on the -C drive.  More would be better but that's as long as the -4 prop clearance would allow.  I can't measure static rpm (plane wants to skid on grass and/or nose over) but climb RPM is at 6200 at 120 mph (up from about 5200 with -B drive) and VSI is pegged (hard!).  Only did very brief test of WOT in level flight and engine hit 7050 rpm.  IAS was still climbing at 215 mph.  Oil cooling has suffered due to stalled air around prop hub and reversed spiral of airflow due to RH prop.  Erased several years of tweaking inlet shapes.
 
Most unexpected finding so far is the radically improved glide at idle setting.  Have no clue why.  Would have expected worse instead of better.
 
Tracy