Thought I'd give this mod a try, and I too am getting issues with memory use. 4 GB RAM, with the few programs I have running along with KSP, it idles around 77% used. Once I try getting something flying, it goes up to around 85%. I've noticed with some other games, getting to around that percent is risking the game just crashing. Been pruning off parts I wasn't likely to use to try lowering that use percent. To compare, before I added B9 to my mods list, the memory useage percents were about 10 less. Hm.