Quote Originally Posted by cradeldorf View Post
I'm not real sure the entire cabinets were flexing but the back panel was sure making a racket maybe if I did some heavy duty bracing on them they'd shut up. They are about 24" by 30" 1972 particle board that I swear looks more like 5/8 instead of 3/4
Bracing, doubling [or tripling if 5/8"] the panels are obviously required if they flex and if the rest of the cab isn't made from at least 3/4" no void marine grade, BB or Apple ply with at least one 'X' brace, then it's probably flexing too, or if not, will be when the back has been sufficiently stiffened up to transfer the air load to the next 'weakest link'.

GM