Oh good, I was hoping it would be that. You are right that the range is not sufficient so here's what worked for me. Adjacent to the trimpot are two 10K resistors. Ignore the one that's by itself and tack a 27K resistor across the the one that's on the end of a group of four (can't read the number as it's under the part). That gave enough range to dial it in.

Thanks for that info Dieter!