@Ferram4 I am quite sure this is a bug, but whenever I have cargo bays from B9 Aerospace pack, and I put a battery pack on the inside, it increases the drag of the craft a bit. I don't think it should do this since it is shielded by the cargo bay doors. I have put a poop ton of batteries on the inside of the cargo bay, then I checked the mach lines in the popup in the SPH, and saw it was really high amount of drag (the red line I think is drag through different machs?). So I removed them, and rechecked the red line again in the popup window, and it was SIGNIFICANTLY lower, even though everything should be shielded. Is this supposed to happen, or is this a bug?