We did a similar trip this September, paddling Flaming Gorge dam to Ouray adding on to a Lodore trip. (We had done Ouray to Sandwash the year before adding on to a Deso trip.)
Lodore is a great trip but it's a long drive from the west coast for only a 4 day trip. We only had 4 extra days so brought a tandem canoe and a sea kayak for the Split Mountain to Ouray stretch. We put in at the dam in a raft and with steady but easy oaring could do 3.5 -4 mph with 2000 csf being released from the dam.
After running Lodore we switched over to a the canoe and sea kayak at Split Mountain and could average 5 mph
These add on sections don't have great camping, in the 23 miles or so above the Gates of Lodore there is no camping except at a couple of unattractive drive in sites and below Split Mountain there are lots of sandbars but no protected sites.
For those contemplating this mini John Wesley Powell jaunt there are some quirky permitting in addition to the multi-day permit. To float into the Gates of Lodore ramp you have to have a play permit and have to arrive after 2 PM the day before your Lodore launch. To float down from Split Mountain you have to have another play permit and there is no camping in the Monument which is another 13 river miles. We got to Split Mountain after camping at Jones Hole, 19 miles, then had to de-rig our raft, repack our flatwater boats and make it out of the Monument by dark, finding a suitable sandbar just after sunset.
Melanie and River Runner Transport were super helpful with the somewhat complicated logistics, picking up our rig at the dam, delivering it to Split mountain (with fresh ice even), and picking it up again and waiting to hear from for the final destination since we weren't sure we could make it to Ouray in the time we had. We made it to Ouray with plenty of daylight left and time to pack up (sorry no decontamination) and do the all nighter back to Oregon
This trip isn't for everyone but sometimes its nice to pay attention to the ugly stepsister of the more popular parts of the river.