5 year (hard to believe) followup, your bushing mod has been working perfectly for the past 1500 hours or so. Thanks for taking the time to post the detailed info!
I’ve used @gonnasellit bushing spec mod for several years flawless too on my ZD1511 72 SD.
The old pro deck blades with more lift on wings really distributes HEAVY Clippings way better than the wider flatter stock ACS blades