why did exmark go with the larger size 15/16 hole on the last of the ultracut decks. when i bought my machine a few months ago my dealer gave me the regular size blades but when i went to change them i found that i had a different setup than i am used to. has the brass spline with the larger hole blade. what is the brass there to be the weak point? why was it changed for the last of the ultracuts? 566000 is is my serial number.