John, heavier guage steel is bound to help hold heat. I never did a before & after test on mine. When I got the Bandera last April it was a complete rust bucket. I found this site and one of the Brothers hooked me up with his welder friend. The rest is history.
One of the things that I have been meaning to do is add firebricks to either the firebox side or cooking chamber side or both. That's bound to hold heat as well.
Mark - part of Cat Sass BBQ Team. Community Development VP - Secret Squirrel Society (but we don't exist)
Member: Mid Atlantic BBQ Association. Member: KCBS. CBJ # 31818
"Life's too short to drink cheap beer or eat crotchpot BBQ"
NB Bandera - refurbished; Two Big Green Eggs: Poncho - Large, and Lefty - Small; Weber Kettles; 6' fire pit; Super fast Blue Thermapen