Well, what can I say - it works!

I just wish I had the maths ability to work these things out by myself - but then again I do get stuck after I run out of fingers

The readout now shows a clocked RPM of 795 and using your little bit of maths I get a nearest rpm of 800.
Works like a charm!

Now for the fun part, putting the pulse back out on a pin in real time....

Leigh