This is, without a doubt, the best parts expansion that I have downloaded for KSP. But, can I make some suggestions? Some things I've found myself wanting after building with B9 are: a smaller hypersonic cockpit that can fit onto the Mk 2 body, smaller Mk2 - 1.25m adapters (the originals are just too long for my tastes, I often just go without), inline intakes for the Mk2 body, and monopropellent tanks for the Mk2 fuselage system.