Easy getting to Gunnison with a 42 foot trailer. However, staying in Gunnison may have you driving through some good riding areas. Find a place in the most south central area to start and leave the truck and trailer, like Del Norte or South Fork. Then make a loop. I have thought about this a little and here is what I would do if I had a 5 days to ride in Colorado.
Highlights for each day:
Day 1) North Clear Creek Falls. You will thank me for this one. It isn't one that many people see, because it is off the road a mile or two but they say it is the most photographed falls in Colorado and when you see it, you will know why.
Day 1) North Rim Black Canyon. Stop at some of the overlooks to see the depth and ruggedness of the canyon.
Day 1) Redstone Inn. Very turn of the century (19th to 20th that is). Make sure to make reservations. It's Kinda expensive, so if this doesn't work ride on to Carbondale, there are some more economy hotels there.
Day 2) Independence Pass. Everyone does this once, highest paved pass in Colorado. Wear something warm.
Day 2) Glenwood Canyon. WOW! You will not be disappointed. Stop at the scenic overlook and go look at the rapids, class 4 and even some undoable.
Day 2) Hotel Colorado. Teddy Roosevelt stayed here
. Go down to the hot springs pool, just below. Nice to relax in after a long days ride
. Also a little expensive, but there are a number of less expensive hotels in Glenwood as well. Again, make reservations.
Day 3) Grand Mesa. This is where they filmed part of American Flyer with Kevin Costner. Nice twisty but flat. If you have the time and you want to do it, you can take the road out to "The End of the World" overlook. There is a very easy dirt road down off the plateau but you may not want to do it on the big bikes.
Day 3) Colorado National Monument. You may not have heard much about this, but again you will thank me if you get there. It is absolutely amazing and the road up and around is a great ride.
Day 4) The Gateway loop. Actually you would be doing only the good part. A whole lot of local (pirate) riders make this loop through Gateway and stop there for lunch at the little cafe. The Gateway resort there also is where the John Hendricks who started the Discovery Channel has all his getaways offered on the discovery channel. There's a great car museum there as well.
Day 4) Hwy 141. South of Gateway is some very unique rock formations along the Dolores River as well as the Flume used during the 1850's gold rush.
Day 4) Durango. Lot's of places to stay, eat and drink. They have a winery and a brewery.
Day 5) Million Dollar Highway. North of Durango, you may want to stop in Silverton and/or Ouray for a hamburger, as well.
Day 5) South Rim of the Black Canyon. Not as much to see but still some impressive sights.
I would have some other things planned as well, if this were me. But my guess is you may not read all of this anyway.
Attached are these routes in both Garmin (.gpd) format and Universal GPS (.gpx) files.
Just some food for thought.