I Have to agree with Frostiken here, your parts aren't balanced very well. They are brilliant but it is hard to use them. I've tried to make a shuttle that uses your VTOL engines but you need so much fuel to make them any use other than on Kerbin, therefore you need more VTOL engines. There are only so many you can cram on before your ship destroys itself or uses all the fuel to get off the ground. Maybe you could create a bigger VTOL engine for the larger ships and maybe one that can be radially placed.