Patrick Turner said:

and I use the 4 ohms tap and connect 16 ohm speakers?

This way distortion will be 3 times less, but there is *no* risk
of damaging the tubes or the OPT.
There will be less maximum power.

With triodes the distortion would be less, with pentodes it would be
more.

--
Sander deWaal
Vacuum Audio Consultancy