I have only been part of this sight for a short time. I have only heard of "double blades" here & I guess I have to ask - Are we really talking about bolting 2 blades to 1 spindle? Do they line up any special way? Is this good for the mower? What if I have a mulching setup instead of side discharge? On a different note, Do most engage their Blades at low RPMs? Is this better that at full? Sorry for asking questions that are basic for "Lawnsiters"