The 15 degrees came from Hucho's book originally but was posted here in this forum.
I am guess I am going to have to wing it I don't have access to such a book. I figure that anything is better on a sedan or coupe anyway. I think I will go with 6-7" range. It won't hurt to try. If it doesn't help, I'll take it off and sell it. It's going to look cool after I am done. Somebodies gonna want it.
Oh well back to work. Got one side of it done already. The other side will be faster, I know what I am doing now.
