Exhaust stack help

Soo need to put a taller stack on the truck it' just too #### loud! You will see in the pic the outlet is right near the window so I am going to change out the stack with one thats 12" taller which will be the same height as the back board for the flatbed. Soo should I put a miterd or turnout like I have? Need to get as much exhaust noise out of the cab as possible

 

From the ground to the head board is 10ft. I do local deliverys so I park on the side of the road under trees so u don' want to put too tall of a stack and it get banged up

 

I have a mbrp quite series muffler under the cab. I gonna put a stack thats 12" taller but need to know if miterd or turnout would make a sound level diffrence in the cab