the bikes I own all have cranks that are either 172.5 or 175. Although Im not short, I've wondered if shorter (170 lets say) would be better for my more natural higher cadence.
Like you, Im not fast, and 10mph, 16 kph is more the upper limit of my usual avg speed over a day, often lower in mountains, but my skinny legs are not mashers, so a faster cadence than others like just works better for my knees.
The thing is that Ive never had the opportunity to try shorter cranks, and the 175 crankset on the bike that Ive spent the most on touring the last few years has been fine for me....so I dont see myself changing it just to try it out.
Maybe my cadence with the 175s is a bit slower instinctively than shorter ones, but I cant say I feel a diff between the 172.5 and 175....

whenever this topic comes up, I think unless someone has the unlikely opportunity to change out cranksets easily on the same bike, so that fit and everything is a constant, its probably not easy to get proper answers.

I know you dont use spd cleat shoes, but a few years ago, I moved my cleat position slightly that puts my foot more "centered" on the pedal , it was feeling like I was "tippy toeing" too much before, and this helped with getting more slower cadence torque into the pedal....dont know if that is explained properly, but this may have helped with the 175 cranks Ive used a lot lately.
Also, I dont have a cadence reader thingee, so the times I have figured out my cadence for an idea, it was while touring, usually going up a long hill, and just counting for 30 secs or a min, just for something to do, and for climbing with a heavy bike, 80 rpm is about what my legs prefer, maybe 85, just less torque on the knees.