I installed a JAMO aluminized 5" straight exhaust on my 15' LML a couple months ago, installation and fitment was right on, sounds great as well. My biggest concern is how it will hold up to corrosion, I'm in Wisconsin so lots of salt on the roads in the winter. Probably would have been better off with stainless steel but oh well, I could have also painted it but we'll see how it does.
I bet the aluminumized tubing will hold up better. Stainless looses some of its corrosion resistance as the temperature increases so long term its likely to still discolor from the salt.
2015 Chevy Silverado 2500 HD 6.6L LML