I have to commend you as well, Phil. For your first two pies on steel, those are phenomenal.
Regarding the pre-heat... 540 isn't horrible. If you go with a 2 day cold fermented dough, you'll end up with more residual sugar, the crust will brown a bit faster and you'll be closer to the 4 minute bake time, which, for me, is just about right.
And, this gets into pretty subjective territory, but, if you're making this pizza for company, you might want to dial back the bottom coloring just a bit- which will also help with your slightly lower stone temp.
What flour are you using?