I currently mulch with a JD 717a, with a mulch kit and G6 Blades.. Never leaves a clump. I like the cut. Plus it only has a 19hp engine. I have heard some mowers need more HP to mulch. Let me know what combinations you have. Looking to buy another Z and interested in hearing your experiences with different mowers, on St. Augustine grass. I like mine but not real happy with the local Deere dealer. So open to make a change.