I asked for a critque so I appreciate the comments!

@Dave
I don't have any _strong_ reasons for not using bash, but it boils down to:
- Most of the limited scripting I do is on Raspberry Pi and other SBC type devices, usually with Alpine Linux, which out of the box has /bin/sh as a symlink to busybox, so I work with that in lieu of installing bash.

- I sort of like the extra challenge of not using bashisms, even if it does make things a bit harder/uglier than it needs to be.

I'm at a loss to explain where I came up with the triple parentheses for incrementing i.  I just tried it on busybox and two seems to work fine (though three does also).  The ++ form does not (as you note it would require bash) though I'm familiar with that form, it just doesn't work within the constraints of busybox.