Slide rules

I'm playing with making slide rules. I welcome any suggestions for useful radio scales. Here's the current version... which I used to generate this N600-ES-ish slide-round (pdf).

So far:

slide round v3

variation a
variation b/c front/back

slide round v4 - interactive/script-driven
slide round v4.1 - with a good working example
slide round v4.2 - with loadable examples
slide round v4.2.1 - more examples
slide round v4.3 - polished a few items
slide round v4.3.1 - minor code tweaks + nice example
slide round v4.4 - front and back in one SVG for easy printing - print in landscape mode to get something like this (pdf).
slide round v4.4.2 - featuring N600-ES0ish example - probably the one I'll try to build. needs more work though
slide round v4.4.3 - enhanced spiral, like KL-1 but with L scale added.
slide round v4.4.4 -even better spiral - the one I actually built! I should upload some photos of it.

Here are a couple photos of the slide-round I actually made. It's inspired by the KL-1, so the back rotates with respect to the front and the additional indicator on the front shows the position of the back index. But this has a couple extra scales compared with the KL-1, so is a little more useful, if also quite a lot less beautiful.

Maybe I'll make a demo video one of these days, showing how to calculate dipole length, or something.