Duncan is much shorter trail than Ute which would save about 2 miles hiking. He would have to float for about 3/4 of a mile farther. From Duncan to Boulder Garden it is a more of a float than one mile. One thing to think about is that it is Stone Fly season and camps are a much coveted thing, especially by the commercial trips, which race to the put in to get the camps that match the bugs. The chance of you getting Boulder Garden is pretty low, unless you plan on being at the register by 12:00 am the day of launch. If you are only going for a two day float then the chances are even slimmer as trips would have already signed up for that camp the day before. I have had a friend hike in mid trip and Ute Park is generally the best spot for meeting up as there are a lot of camp to choose from. There should also be overflow camps that the BLM puts up for the Rubber Hatch that coincides with the stones. Most of them are upstream of Ute but there are a few in Ute Park. Good luck.
I have enjoyed your videos, and candor.