Ah yeah I was meaning to put less engines for my lander last time, but I didn't have fuel lines yet so it didn't make that much sense, could do that now indeed. Yeah I have all engines on at all times when burning, but the liftoff stage wasn't working as 2stage asparagus+boost so I changed it to just liquid+solid boost stage and it got me to orbit with 3800 delta-v left, so I suppose its okay. I have to test that SBR fuel tank trick, sounds awesome