Agreed. I'm not suggesting Inline-6's are bad designs. Actually, they are very, very good engine designs. However, automotive manufacturers don't sell engines, they sell vehicles. When you are designing a vehicle, you invariably have to make compromises. For the heavy truck manufacturers, they have generally settled on I-6's because that configuration works well for them. On the other hand, most recreational boat builders don't like inline 6's. Ski boat builders definitley don't want I-6's. There were even a few I-6 motorcycles out there at one time, but that really didn't go anywhere. For street cars and light trucks, there are I-6's out there, gut they are definitly not as common as they once were, not because they are bad engines, but because the disadvantages of this configuration are becoming more of an issue for the way automotive designs are forced to evolve. Then you have the unique situation of a car that is very much defined by it's engine. Mazda rotary, M3 I-6, viper v10, mustang/vette V8. I don't think a high revving, high specific output I-6 or turbo v6 (for thread relavence) would be such a bad thing. It just doesn't really fit with the image of the car.