Aceman
I am your doctor of love!
As long as the mismatch has the cab at higher ohms than the amp's output it just results in the amp running cooler.
Cooler means darker with more sag, so no harm at all but most will prefer the punch of a correct match,
The amp's output impedance and the cab's total impedance has much less impact on tone then the impedance of the individual speakers being used.
Two 8ohm v30 in series will be 16ohm total, but they will still have the 8ohm v30 tone.
Two 16ohm v30 in parallel will be an 8ohm total, but will still have the 16ohm v30 tone.
Interesting. Never knew that.
Is it a big effect, or only something you notice when running high volume/on "10"