Id prefer that tip to exit on the passenger side if you are set on havin the tip visible - just my opinion tho. Youd like a 22in magnaflow with LTs, I love it on mine, I really need to get pipe ran over the axle tho - it should sound perfect then. 18in would be too much for me I think, when I really step into it with the 22 it gets a little noisy for my taste.
Truck is comin along great man; that shaved gate is a nice subtle touch to the rear, and your truck makes me want full LEDs in my cab even more...