With my 1987x I see and hear the same thing as with my JCM800, with Presence at 10 there is a about 6dB difference in treble compared to the models, so it's not my amps.
The difference in treble response came down to the impedance curve of the Suhr RL.
View attachment 45868
Here are the settings that match the Suhr RL.
View attachment 45870
The followup is thusly, I request a few slots of custom impedance curves so I can save and recall them quickly or use as a global impedance curve.
PS.
The models are spot on, I freaking love my Fractal.