I almost went the diffuser and screen route. It's one of the few things I remember from Martin Moe's book that I picked up many, many (many) moons ago. Ended up grabbing some small interlocking plates instead that are raised about an inch off the bottom glass.
When I first made up my mind to go back to the UGF, my plan was to recreate my first setup by using deep substrate and weak pull. In your experience, is there a flow rate that's too low for reverse flow UGF?
I like high flow as I am not interested in promoting anarobic chemistry. Paul B likes low flow with shallow sand bed at 2” max depth. Both produce good results.