Thanks for the info on the tanks.
I initially pulled only from one tank, but found that it sweated quite a bit, which attracts dirt like a magnet! When I opened the second valve, both tanks sweat, but not as bad. Maybe the manual suggests running off one tank so when you run out of fuel, you can simply open the other valve and not be stranded. When you ask Ferris about the baffle, maybe mention that. I can't forsee any harm in pulling from both tanks.
I know I was bogging in the thick grass prior to removing the baffle.
As for the mixing valve/box, I have no before/after scenario since it was replaced before I purchased the machine. Lou claims it produces more HP.
I think the striper is harmless if you don't have rocks or stringy weeds/grasses. I found it will pull on anything not growing vertical.
Hope this helps. I'm very curious to see what your GPH is once you swap the mixing valve/box.