Not much happening in here, but I give a shot  

I'm really enjoying my Prinzetone, but sometimes miss a more Vibrolux kind of tone.
I'll try a bright cap to get a little more sparkly treble at low volume.

Does anyone  have other ideas for usefull mods?

If only one could put in one 6L6 and pull the other tube... Low wattage Vibroverb in an instant...  

Would the transformer be able to handle 6L6 tubes (rebias offcourse and then use an attenuator) to take the sweetspot volume down)?

I installed a mini switch just below the "Tweed" switch and coupled a 100pF brigt cap to it.
Allthough it is still no Vibrolux, the accute need for one dissappeared in an instant. This mod takes it a long way into Deluxe Reverb territory - and then some. I´d say this mod is almost mandatory!