First thing I tried. Unfortunately you can't. I considered shaping them in a V pattern, but then you have to cross the pipes which is possible but annoying. I also cut out some foundations to reduce weight by this method. Even though it has 5 engines, it can only sustain thrust for one of them, hence the tanks, so maybe 1 engine is better for frequent trips if you can't stock up in time (although ammo stockpiles seems to be the bottleneck in my design).