Yes, if you are into space planes and planes in general , FAR is by far the best mod for you. More accurately calculated aerodynamics mean you can use fewer wing surfaces, making for more efficient, sleeker design. Also, you can run simulations directly in the hangar while building the plane. This is usually enough (at least for me) to nail down your aerodynamics on the first try, and than just iron out any quirks in just a few test flights. I personally have resigned to using the B9 cargo bays for now. I have only installed those parts (as installing the whole B9 makes KSP unplayably slow). Here is one of my newest designs. Using the smallest cargo bay, it is capable of placing a full 1 ton of payload into 100 km orbit. You can see I was testing it on two 0.5 ton RCS tanks. Happy building!