I had an existing 3D model of a supply-air plenum that now needs two key modifications: an access section large enough to slide in V-form filters, and provision for an egg-crate return grille. Your task is to revise the current geometry accordingly and return the finished model to me as a clean, well-layered DWG file ready for coordination with my wider HVAC layout. Once 3D model is complete will require a construction drawing with dimensions. Please tell me a little about similar HVAC or sheet-metal models you have handled before; a brief note on your experience is enough—I don’t need a full proposal. Accuracy around clearances for filter removal and grille mounting is essential, so the updated model must reflect realistic fabrication practices. Once I confirm fit and orientation, I’ll close the project with the final DWG in hand.