I've never handled a Sinsinati gun, and know nothing about them, but I think the more you use it, the more comfortable you'll become with it. As has been stated in previous posts, its the choke that determines pattern spread, but for a gun that is used to shoot cracker shells, buckshot, and slugs, I'd opt for a cylinder or improved cylinder choke anyway. The constriction of a modified choke might produce tighter patterns, but it will just as surely cause those cracker shells to explode inside the barrel. It doesn't hurt the gun, unless it results in a partial bore obstruction and you fire a lethal round before clearing it, but it'll sure make your ears ring.
As a generality, there's an inch of pattern spread for each yard of range, so you'll observe a 10" pattern at 10 yards. Small diameter birdshot tends to do a little worse, and large diameter buckshot tends to do a little better. If you pattern the gun and get an 8" pattern, you're ahead of the curve, if you get 12" its not the end of the world, but patterning the gun with the shells you intend to use is the only way to know for sure. I pattern tested a few brands of 00 Buck a while back, and while every barrel patterns differently, as does every different load, and every different manufactured shell, I was a little surprised just how poorly some patterned and equally surprised by just how well others others patterned. Federal Premium 3" 00 was far and away the tightest patterning, and produced nice round patterns, rather than linear patterns, or donuts, and 3" Heavi-Shot was nearly as good. I was disappointed with Winchester's 15 pellet 3" 00 load, which I expected to produce good pattern density, but didn't, and some old 2.75" C-I-L buckshot I stumbled across was just awful, producing narrow linear patterns.
Considering how your gun will be used, I'd pay attention to whether or not you get reliable ignition from all brands of ammunition. Federal tends to seat their primers deeply, and in my experience, guns with short firing pins don't fire them reliably. In the days when that as all I could get here, it proved most disconcerting to hear a click when I expected a bang.
Once it as determined that the gun fired reliably, adjusting the length of the butt stock to fit, and installing a good quality recoil pad will improve the manners of the little blaster. Then I'd ensure that the gun shot to point of aim, and that I could easily see the bead against all backgrounds, and in subdued light. An XS Big Bead might be a worthwhile expenditure, which just glues on over the factory bead, so doesn't require gunsmith installation. I wouldn't discount the advantages gained through the installation of rifle sights particularly a ghost ring and post arrangement.
I'd silver solder a barrel band sling swivel to the barrel, even if it means shortening up your forend a bit. The clamp on swivel bands in my experience tend to slide up and don the barrel after firing a shot or to, but epoxy could make a satisfactory job of keeping the clamp on barrel band in place. Aside from making the gun more convenient to carry, a sling will help to ensure your support hand doesn't get out in front of the muzzle of the short barrel.
Nylon butt-cuffs are an inexpensive way to keep shells with the gun, but they are the least durable option. If you like the look, a leather one is better, but until broken in takes a death grip on the shells. I'd be inclined to screw a sidesaddle to the off-side of the butt. The disadvantage of butt-cuffs and screwed on sidesaddles is that it prevents shooting the bun ambidextrously. A shell caddy could be worn on your belt which provides quick and easy access to your ammo. I like the vertical, hard plastic 6 round caddies from California Competition.
Edited to add . . .
So I had a look at the on-line adds and photos of these guns, and they don't look bad. One concern I have, particularly with magnum loads, is the action release spur behind the trigger guard. This looks like an injured finger waiting to happen. If the action can be released by pushing down on the inside bottom of the trigger guard, that to me is a better option, and I'd have the spur removed, or moved to the bottom of the trigger guard.
IMHO, a fixed barrel band style sling swivel is a better option than a forend attached swivel, if the forend retainer is spring loaded. If the forend is held in place by a mechanical lock or a screw, the swivel forend attachment is fine.
The vent rib is a nice touch, and provides hope that the gun shoots to the point of aim.