Hey guys. I know I'm way late to the game on this post but I can't find any other puller rocket discussions. You can actually have fuel drain from the bottom up using the fuel lines. I run them inside the stage separators on what I've termed the "gangles." It's a great way to reduce weight as you ascend since you can dump empty fuel canisters off the bottom of the stack without dropping any engines. The gangles don't experience compression forces and can be strung to improbable lengths. A few control surfaces and disabling the engine gimbal till the gangles reach a shorter length are all it takes to make it stable. More gangles tends to make for a more stable rocket too. I've found personally that I can build much larger rockets in the puller configuration than the pusher. My current design, excluding all stages above the main engines, is the equivalent of 20.25 of the large orange fuel tanks. I'm still experimenting with engine configuration.
