@Chazrox Ok, I figured out this much....
I needed to declare the Convolution reverb module (ScriptnodeFX) as and 'AudioProcessor' instead of and 'Effect'.
Then I could use:
Convolution.setSampleRange(min, max);
then, use a knob to adjust 'max' value.
One thing I can figure out how to do is, after loading a preset or scrolling through reverb presets, I need my 'Length/Time' knobs 'max' value to change to the currently loaded files 'sampleLength'. For some reason I can only get it to load upon recompiling.