I'm going to put a disclaimer 'cause what I say and you attempt this, its your own doing :
I read somewhere you could pull two of the power stage tubes and they have to be either the inner two or the outer two if I'm not mistaken. You do not stagger them.
But its best that you pull both 5U4 rectifier tubes and replace it with an 5AR4 in either socket.
The output jack what was for 8 ohms load is now 16 ohms if I'm not mistaken. Same for the 4 ohm jack is now 8 ohm tap.
Now I don't know if you could do this with "silicon diode" rectifier.
Now that you are using only two power stage tube you could crank up the amp because its 50 watt and push the power stage tubes. Uh, it doesn't necessarily sound like a 50 watt amp because the output transformer is a 100 watt OT not a 50 watt OT. There's some "mojo" in the OT to sound like a lower power amp.
Yes, I've done the above. Taste may vary.