Differing Shaft-Butt Diameter – Deal Breaker?: original inquiry on GolfWRX on 03/23/2019
You appear to have a firm belief through knowledge and experience that once a grip size is determined for you, the same size should be used on all of your clubs (not really counting the putter) in order to play your best.
This is a major, debilitating flaw in clubfitting process that is hurting and limiting you, and just one of numerous elements that helps differentiate between clubfitters that are able to get the most out of one’s swing and game and clubfitters that cannot.
The bottom line is are you more interested in having all of your grips feel the same size to you throughout all of your clubs, or are you more interested in playing as well as you are capable of? These are very different priorities that can actually conflict with each other.
Evidence of how to competently fit for critical grip size goes back to at least the middle of the last century. If you have never properly learned this skill anywhere, you might consider a qualified, paid clubfitting consultant to help guide you through the process.