Ah yes, thanks @ProjectileObjects - that did the trick!
Circling back under a bit less pressure, the simple answer is “watch the video here”:
If we want to avoid having extra, intervening sliders in play we can apply a Do Math function on the receiver like this:
(($MAX - $MIN) * ($VAL - src_min)) / (src_max - src_min) + $MIN
I’m not sure if you can define the arbitrary variables for src_min and src_max so we may just have to hard code. In my example, if my source range is 0 -> 0.85:
(($MAX - $MIN) * ($VAL - 0)) / (0.85 - 0) + $MIN
There are also a bunch of built in functions available as defined here:
https://github.com/davedelong/DDMathParser/wiki/Functions
Hope that helps someone else 