Dyna comfort....Is there an answer?
 

I'm currently riding a 2013 Switchback with a Mustang Vintage Wide touring seat. Had a 2012 Fat Bob prior with the same "issues". I'm 6' 225lbs.
Yesterday I took the the first long ride of the season and it was very typical of how I ride(except my 11yo daughter's plans got messed up so she rode with me). The ride was ~250-300mi starting out at 9a and getting back at 5:30p, all country roads though the towns and farms of northwest CT and eastern NY. Short ride to the meet-up and breakfast with 3-4 other riders, once riding we make stops every 1 to 1 1/2 hours for coffee, change of layers, lunch, fuel, taking a leak, etc.
My point, the Mustang touring seat is considered one of the most comfortable seats available(mine is broken in at 2.5k+ miles now) and I fit good in it. Why is it that even with freq. stops and relatively low miles, toward the later part of the day my ass is killing me? My daughter who's all of 90lbs had the same problem on the back.
I hadn't ridden for 12years before getting the HDs but rode for 20years before the break and I don't remember having to "tough it out" like this when riding before. I've spent stupid money on different seats between the FB and SB and none of them have been comfortable to a greater or lesser extent for my typical riding. I have some longer trips planned incl. one 3 day with my wife and I don't want it to be torture because of the lack of seat comfort.
Is this just how it is with HD or my fit on the Dyna? I don't want to but would moving to a touring frame HD be any better?

It must be either the seat or the way you sit on the bike....I'm 6'2" and 290 lbs and have no problem knocking out a 500+ mile day on my Dyna.
A touring bike would possibly be more comfortable, but I have owned a few of them and haven't noticed a big difference in comfort between them and my Dyna.

I have a couple of seats that I switch back and forth for mine...One is comfortable on long rides and one is not.

I also have the Mustang wide touring seat with no problems.
Have you switched the footboards to forwards?
Perhaps a backrest would help keep your back more vertical.

PaiN...??? How old are you? That could be a big factor! Or it could be the shocks on your bike? The shock settings? Many personal and bike related possibilities. ???
...Suggestion... if possible try to switch bikes with someone and see if there is any difference???
I am 6'1" and weigh about 245lbs dressed. I have ridden my FXDC 300+ miles in a day and had no pains even with the stock seat. My searching for another seat was to help my wife as a passenger and possibly to elevate me or move me back, just so I would have more room on the bike. I love the FXDC but feel a little cramped with the mid controls and the shocks are not real cushy.
Just random thoughts that crossed my mind?!?

I also have had problems getting comfortable with the mustang with backrest, have tried other solo seats, and not had any luck finding the right combination, going to try a 2 up Harley seat next either the touring or sundowner, ride solo 100% of the time and have a rack for the bag I use, figure I can sit the bag on the back seat

Ive taken the bike below (mustang seat) on 300 mile days, I didnt have butt burn but would notice my ass talking to me. Last Friday I did an Iron Butt 1000 miles in about 21 hours. Just about every part of my body hurt........except for my ass. I was wearing some padded bicycling shorts. Im positive they did the trick and Ill be wearing them on all future longer rides.

I'm 46, physically fit, no low back or serious bodily injuries. So my discomfort is not caused by any physical problem.
I hate to bitch like this but its the second bike(The SW is much better then the FB), God knows how many seats and its really taking the enjoyment out of my riding. Like I said in the OP I don't commute with the bike, when I ride its usually for the day or more.

I ride a 2010 Wide Glide with a wide Mustang Touring seat. I used to have the same problem until I bought a gel seat cushion from JPCycles. Last year I took it with me to the US and rode 8,000miles on a Fatbob and was bloody glad I had that gel cushion with me. It was worth the $90 I think I paid for it 10 times over.

Airhawk is the answer. http://www.airhawk.net/airhawk-products.aspx

I use the medium cruiser size in Airhawk not Airhawk 2. Original is a litle more expensive but worth it, Made out of inner tube type material so it has some give to it. This is hospital bed technology. With these there is no worrying about having to choose between a good looking or comfortable seat. Just throw one of these on what ever is your good looking seat. The seat itself makes no difference because your floating on air.

I'm 64 and can do a 12 hour day.

Ill vouch for the HD Sundowner two up seat. Looks dorky on my Fatbob, but its simply fantastic for longer rides or days when really in the saddle. Im 5'5" and 220. My butt does very well at the end of the day.