Thank, ahoeben
I'll give it a try though my programming experience is a fair way in the past and even then limited to machine-code, 8080/Z80 assembler and the simpler higher level languages. Definitely not the C-varieties. Hopefully I can plug in a number, recompile by rote and replace the appropriate component of my setup without affecting any of my other settings.
Certainly a very reasonable, definitive answer though!
Edit: I think I went off half-cocked there. Having looked into it i think now that i simply edit the version of SettingItem.qml that I already have in myResources/qml/settings directory.
Would that be right? (Sorry to be so "newbie")