I have a Small Business account as well, but only use it when shipping long guns or other stuff too large for flat rate boxes. For the small stuff I have switched over just buying the boxes, as it has always proven to be less expensive than the shipping charge figured out on the CP calculator. Just because you have the Snap Ship option doesn't mean you must use it for everything.
Yeah, the lack of optional insurance beyond $100 can be a concern for some packages. And the recent increase in oversize charges is a killer. I still have a bunch of U-Line boxes and original manufacturer boxes that I use for shipping, but I always break down firearms to make them fit under the 1-meter length and then re-cut and re-fold the boxes I have to squeeze under the maximum. It can be a PITA but saving the oversize charge makes me feel better.
A shorter/wider box would appear to be less firearm-like and hopefully less likely to attract unwanted attention and possible vandalism while in transit. And I don't have stats to prove it but I'm sure that it would be less prone to accidental damage as well.
I know that's the answer...but in many cases (like this one) it's easier just to remove the impulse item and carry on.
The odd part is that in the past, I would tend to snoop around a website in case there were other items I might want, which could be added to the same package and would thus save me shipping overall.
Now...it's quite the opposite. This tiny box containing a couple small items will cost me $X to ship...but if I remove an item or two, the same tiny box will cost less. It's not weight...the entire order would have amounted to a few ounces. A by-product of our reliance on automation and computers? Poor policy decisions at the retail level? Doesn't matter what the explanation is; the upshot is that it will cost businesses some sales.