Hey Dave, so if you just mounted up the deck as it stands you would be running a bit hot on blade speed? 6/5 wound get you around 20% over in blade speed? I have a similar dilemma with a blade I bought for the SX 60. It appears not to fit but the only way to confirm is just removing the deck and see what, if anything needs altered. I researched it before buying and at least one web site indicated it was a match for the Zeroturn.