Hi Paul, Our tech is out of the office today so I will try and help you. I was the tech a few years ago until I changed departments. The 99-917 Gator Mulcher blade was made for the Snapper Commercial walk behinds. It is NOT a flat blade. There is a drop of a little over 1/4" (.297). The person that said they were using some Bobcat blades has either a different year or model from yours. I don't remember which is more current, but Excel made mowers that used a 5/8" center hole and Bobcat's are also 5/8". From your earlier posts, you have a 1/2" hole which is less common. I have heard of guys successfully doing the stacking you are considering, but we have to advise against it for safety reasons. If you do attempt it, be darn sure the blades clear everything under the deck and check your deck, spindle and blades for any signs of stress or failure on a daily basis and replace as necessary. Keep in mind the extra stress could excellerate wear on the bearings.