I bought a zt2 54”. Mulching blades are 18.67” long. The pet number for mulching blades is 942-05056-x. If I used blades that are 1/2 inch shorter, like 942-0677b gator blades, what difference will it make? Or other blades that are 18.5” long, what’s the difference? (Besides .17”?). Will the end of the blades physically be closer to the ground because of their shape at the ends?