The outputs on the the amp say 4ohm min. and 8ohm min.
This suggests to me that it might be ok to use a 16ohm speaker in the 8ohm min. output.
Anyone think this is hazardous to the amp's health?
Did a little lookin' around, because I wasn't familiar with that model. The quick answer is NO.

Typically with tube amps, you want to match impedences that the transformer is designed to operate at with the load that is on it. (Says 8 ohms, attach an 8 ohm speaker or cab).

With solid state, this is not as crucial. You MAY be able to get by without matching your impedence, but I strongly advise against it.
8 ohm is nominal impedance. It is just convention. A speaker may be 9 ohms, it may be 8.5, but it will still be labeled an 8 ohm speaker.

If you put a 16 ohm, you are putting twice the load it was intended to carry. It's like trying to haul a bass boat with a motorcycle. It might be able to handle, but I'm not going to risk it.