One thing i didnt do is try different tubes at different spot, dont know how it responds for that but i know that some people did that in the Mesa Walkabout with succes so it might be worth trying...
Cant be arsed to be honest so if you do let me know how it works out...
That is definitely true too. In my ampeg I have Tung sols in the first couple valve positions since they're driven the hardest by the amp, and then JJ's in the rest. That works pretty well for me. Also, experimenting with different 12ax7 type tubes is a good idea, like using a 12au7 can smooth it out and lower gain if that's what you're going after too.