Looks good. But here is a simpler way( I did this in my UDS). A few inches above my fire basket I drilled 3 grate holes. This gives me 3 levels inside my drum. This 3rd level can be used for a diffuser and I can set my fire basket on it. That makes my upper levels now grill time.
Ron, 1 little Chief top loader, 1 UDS (90% built) 1 mini UDS (in plans)