Yes, a classic blunder in CT/Striker and MT design sequences is you can only make belly and deck flat so it takes a tremendous amount of armour to protect those faces of your grav vehicle from weapons like proximity mines or remote-controlled mines (aka IEDs) which can attack grav vehicles over-flying them. Likewise for speeders at altitude that may be engaged from far below.
If you want all sides, top and bottom sloped, then just design the vehicle as a rectangle and fly it leaning 45 degrees to the side.
Or design a shell half the actual height with sloped sides and no bottom and mirror it (double the cost, weight and spaces).