Thank you for the very prompt reply.
I do not have any worthwhile experience with fuzzy logic so I am not certain I would be of any use to you as a tester. I expect you would be better off with someone with a great deal of knowledge and experience with fuzzy to make the testing process more meaningful and any results obtained more useful to you. However, if you need someone for basic look and feel testing I could perhaps be of some use.
Seems like the delta increment is set to 1% of the range value at present. It sounds like the near instantaneous feedback from Qslider to the QDoubleSpinBox is the culprit. This may work OK when you are sliding the slider but is a pain following manual data entry. Sounds like the feedback needs to be deactivated only for manual data entry cases, if that is at all possible. The up/down arrows probably complicate matters here. Could there be a tick box somewhere to temporarily deactivate this feature? This box would NOT be ticked by default and could reset to inactive every time you switched to the control screen.