Probably depends entirely on the trip schedules for the companies, and you would be charged for the days you were there, especially if it required them to have an extra boat for the whole trip. What days exactly were you thinking? Seems like getting in touch with some Moab or four corners locals would be your best bet - send me a PM.
“May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view. May your mountains rise into and above the clouds.”-Ed Abbey