I have a 7-year-old rear engine 1252823 Snapper riding mower. I have two blades: One is a mulching blade. It just fell of when I removed the nuts and bolts. . Now I'm trying to put on the other blade. I can get it almost in place but not quite. The blade seems like it's too long, but I know it is not. There's a trick to getting it to clear the bottom lip of the blade housing. I did it last year, but I can't remember how.. Can you help?