There is a lot talked about gun fit .A lot of people have strong opinions as to what they want ,as do a lot of instructors who have there own ideas and think you to should have them too . Every one is different so guns like clothes are made to fit the "average " man . When gun fitting it is important to listen to your customer and ascertain exactly what is his problem ,weather it is actually gun fit or dose he think he needs his gun altering . Incorrect stance and mount are often in my experience 50% of the problem .
There are no hard and fast rules and so part of the "fun" is talking to a customer ,looking at his physical shape ,height , weight , width of shoulder , length of neck , length of arm upper and lower , slope of shoulder , Etc.Etc. Then look at the gun to its current set up length ,drop , cast . Discuss the sort of shooting that he is going to do mostly and finally what actually is the problem . After that you just have to work out what he needs ,what he wants ,and what can actually be done to the gun in question.