Clothing affects length of pull, not drop or cast. Those dimensions affect where the gun shots relative to where you are looking (high/low, right/left). 1/4" change in drop or cast moves the pattern approximately 12" at 45 yards.
If the gun doesn't fit, you have to adjust yourself to the gun, which means that you are less likely to mount the gun and shoot consistently every time. You can adjust the gun to you or you can adjust yourself to the gun - it is your choice. But if gunfit didn't matter, I don't think clay target shooters would be bothering with adjustable combs.
98% of the time, it is a relatively low cost, no hassle adjustment. I unfortunately am dealing with a gun in that 2%.
