Ray- I sent a PM to you. In looking throught the MMM manual, it doesn't specifically say so, but I do believe (see tx2310's first post above) the 3PH has to be free to move up & down with the mower deck, regardless of whether anything's hooked up to it or not. (BH off, of course.)
Again, if the lower speed control knob isn't open, the hydraulics won't operate for lifting. In the pic below (experimenting last summer), you can see the knob on the right side of my tractor, poking out from the transmission area between the two white safety stickers under the seat.
Please post some pics of your set-up-- I'd like to see your bagger system!