I used !/4" plate for mine. I got the idea turning mine reverse flow after ChromeSporty had his redone. here is the link to mine. It works great. I have seen a friends who has a pipe with hole through out it running the length of his cooker that is welded into his firebox. I dont know how good it works compared to having it done the same way as the langs. which is basically the concept mine is. I dont see how u would get even distribution of heat with just a pipe and then your exhaust on the firebox side. Mine has a plenty of pics of the build
HALF DIAMOND RANCH BBQ
Home made 5' reverse flow smoker
Weber Kettle 22 1/2" silver series
Weber Copper Smokey Joe Gold 14.5"
GPS trackable RED super fast thermopen