Vehicles components and suspension

Hi, I was looking at making a bones for a vehicle and with no mesh and then in ue4 I was going to add sockets and attach the meshes to them and have the blueprint have a bool to make the meshes visible so the players can select how they want there race car to look. but I have tested it in 4.4 and also in the preview 4.5 advanced vehicles, but I get a error. you can add components with characters but it seems you can’t with vehicles. following all the tutorials on youtube to see if the error is me not doing it right but that isn’t it.

Also with the suspension setup, I’m trying to do a Sprintcar game and a sprintcar has 3 different size wheels. I tried to giving each wheel with a wheel blueprint but with the rear wheels being larger then the fronts it make the rear of the vehicle look unrealistic higher then the front. I tried to set the suspension neutral position in a negative position but it didn’t change it. So how would I get the body to sit flat and have the suspension look uneven. Also how do you change the ride height other then suspension neutral position. Also the suspension damping is there a way to do bump and rebound and using a float track to do it. Also can the same thing be done the the tires grip and wear. so in a racing simulator game the tires are cold and as the temperature of the tires goes up with friction the tire grip increases which reduces the tire slip but also increases the wear. Looking at the physx SDK they are floats but can ue4 do them as a float track.