Yeah, that dimension has to be with the discharge chute down. There's only ~1" overhang on each side, past the blades. On the trim side you've got the airgap, deck thickness with reinforcing rib, and plastic bumper. The discharge side just has the airgap.
The oversight I see is trying to stick that much mower in a 6' trailer. You better measure your door opening to verify it's width. You're only giving yourself ~3" of play on each side, if the deck were only 66" (but, it's more like ~68"). I know I can't get my machine up the ramp and into my trailer that accurately. Furthermore, I'm not sure I'd want to even deal with another 6" of deck width in my trailer. I think 60" (~62" measured width on mine) will be about the max limit for your trailer's width.
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Last edited by ducnut; 11-12-2013 at 06:41 PM.