Have managed to successfully bbq pork ribs on my smoke hollow bbq. Pretty good , 250f over coals Rodney scott style.Was a real pain to keep temperature low enough ( coals too near grill level) so thinking of building a bbq pit ( not a smoker/offset). where you slow cook over coals. Lots of YouTube using hollow cinder blocks in the isa but wondered any reason I cant use standard medium density concrete blocks ( not hollow) as I have access to some?