If you can, try several fowlers in different gauges. My only reluctance in endorsing or promoting the 16 gauge is my concern about the availability of wads. The 16 gauge is almost dead as a modern cartridge gun, and, while I certainly agree with Mr. Brooks, and others here that it is a fine choice for many hunting purposes, I worry about finding molds, wads, etc. They are out there now, of course, but for how long?
I have seen many fine cast bullet molds dropped from production by Lyman over the years, and in fact had to order one old Lyman mold I had sought for many years from Ray Pine( Rapine Molds.) It cost much more than the Lyman mold blocks would have cost, but his mold is excellent and second to none. Several years after I bought the mold from Ray, Lyman began making that mold again, for a few years. I understand its now gone again.
My gunmaker left a bit extra wall thickness in my fowler barrel, and even at 30 inches, I don't feel that the gun is bouncy, or whippy. I don't have any trouble with follow-through. Its not quite as heavy as my Remington 870, but it carries well, and shoots well. The 36 inch barrel will point a bit better, but I would feel a 42 incher would be a bit of a drag to be swinging on crossing birds. AGain, these are matters for personal preference, and I refuse to argue with anyone who prefers the longer barrels. I met a man who insists that shooting his 48 inch barrel is the way to go! When I tried his gun, it was too front heavy for my taste, but he hit his targets with it. And, he seemed to be able to push that barrel around fast enough to catch those crossing targets. That is why I don't argue with anyone about their choice.
I never hesitate to let someone who is " shopping " try any of my guns I have at hand. Other friends were nice enough to let me shoulder their guns, and even shoot them when I was first " lookin' ", and that curtesy allowed me to make a much more informed decision on what to buy.
I wish you well. :hatsoff: