Hey, no problem!
I really think that too much importance gets placed on impedance matching of output tubes to speaker load, though. The ideal impedance that's listed in tube charts is part of a much larger acceptable range...much, much larger. Bandwidth and linearity are affected by playing within the range but in reality, guitar amps are neither linear or bandwidth optimized...nor would we want them to be.
The potential issues and the root of the cautions that abound these days are founded in fact but they never get mentioned...so I will. A higher load than the median (published) impedance isn't going to create a functional problem; a lot of old audio amps (juke boxes are a great example) used different load taps to limit the overall volume of amplifiers. The issue arises when you go lower. In most cases the output transformer has no issue with a mismatch in and of itself...the problems set in when the lower load offers insufficient damping to the power tubes which can cause them to arc internally. Old Marshalls were really bad for this as were most EL34 powered amps. EL34s are really reactive in comparison to 6L6s...6V6s fall somewhere in-between. Put a set of 6L6s in a 6L6 amp and say, bias it to 32mA...at full signal, the individual tube current will peak around 120mA. Now insert a set of EL34s in the same amp and bias them to the same 32mA; the individual tube current will peak around 220mA...quite a difference. This is at full signal. This is why screen limiting is so important and also why 6L6 amps typically use a 470ohm screen resistor and EL34 amps typically use a 1K. Those early Marshalls that started all the impedance mismatch talk had NO screen limiting and an impedance mismatch would eat an OT in no time at all. A modern EL34 amp with EL34s installed,set at 32mA bias current will have a peak current of somewhere around 180mA. 6L6 amps with extremely low screen limiting...such as Peavey 5150s and 6505s, also peak around 180mA.
