You can make gun fit as simple or as complicated as you want. The best shooters tend to keep it simple.

I'm fairly new to trap, and attended my first Grand American this summer. During the shoot, I consistently shot well below my average, so a squad mate, a nice gentleman from Alabama, sensed my frustration and suggested I visit a stock fitter who was a Grand vendor, "Country Gentleman," who is also from Alabama. I knocked on his trailer and we spent some time together, a couple of hours, I think, mounting the gun and talking about what I was seeing on the range. He could see my problem and had a solution. I left the gun with him overnight so he could do the work. He added an adjustment device to the stock and made some other changes. The next day, he spent another hour or two tweaking the fit, having me practice my new mount, and finalizing other changes. Even though he didn't have time to see me shoot in that setting, it turns out that the changes he made were spot on, and after a few hundred rounds I was shooting better, more comfortably and more confidently with the adjustments. And, it was a few hundred dollars, rather than a few thousand.

https://www.gunfitter.com/

I drove two hours over to the Alabama Mississippi state line area and had my Beretta 686 Frankenstein gun fitted. I already had an adjustable comb so I just needed an adjustable pad added and fit to my LOP. I arrived at 6PM and after several measurements left at 9PM with a gun fitted to me. Cost was $250

Wasn't rocket science just someone who was good at their craft.