I assembled a similar system using a 4" downpipe into a 4" 2-way T-splitter finished of with a pr. of Geno's 5" chrome tips.
Exhaust exits just beyond rear doors and Nerf bars, tips extend 1. 5" from side of cab. So far, soot has not been an issue. Only downside is front of tips get dinged because I don't have front mud-flaps.
If interested, I'll have to check paperwork at home for the website I got the T-splitter, 4" straight pipe, stainless band-clamps, and downpipe from.