Sundowner seats are like the rest of the HD seat line, after a few hundred miles your back in pain again. You did not mention your stats ie height weight inseam.
IMHO that the finest most comfortable seat made with a real warranty is the Russell seat , each seat if custom built to your stats. Also the Russell does have a spring in that t goes crosswise to support your hips. They can build just the riders section or both the riders and passenges to each of there specifications.
Russell stands behind there seats and will fix it for free untill your 100% satisfied. The only drawbacks are that they are not the best looking seats in the world but are certainly the most comfortable.
A little test, look on Ebay and other classified sites and see how many used Russell Seats you see for sale, if your lucky you may find one. Also if you ever decide to sell your Russell seat you most likly will get all of you money back.
No try that with any HD seat and look on Ebay and see how many HD seats are for sale!!!!!
Next would be the Corbin again they do offer a little adjustment on how you want it built which is a plus. Customer service is not the best and certaily no returns, but Corbin does offer 1 free adjustment.
Mustang seats, well built but they offer no custom builds. Either the seat fits you or not. If your a big guy like myself 6'03" 32" inseam and weigh 270lbs the Mustang is not what you want.
I bought a Corbin tour seat and had them custom build it to my stats, so far I'm neither impressed or impressed, but at least the seat has me moved back to a comfortable position but wether it will comform to what I consider a comfortable riding position........
HD should be shot for the crap that they call a seat and especially the stock ones.
FWIW a URAL seat is probably pretty comfortable if its rock hard like the old BMWs , it seems that the softer the seat the more pain it caused. Stay away from those miracle cure seat inserts be it air or gel as they are usually a waste of money.
One company that I have yet to try is the Seargent Seat Co in Fl. They do offer so interesting builds and have been in business for a long time......
Lower back ache not only could be the seat but could be caused by the cruddy OEM handlebars also. So that is somthing else to think about!
I was wondering if I can capture some knowledge from those in the know.
I do not find the stock seat on my Road King Classic uncomfortable but I have been riding a Ural Russian Sidecar rig for 2 .5 years and haven't done over 90 straight miles on the RK. I do get lower back ache so am considering a drivers back rest.
I am thinking of a riders back rest for the stock RK Classic seat and wondering if people think that the stationary back rest is good or is the adjustable rest worth the xtra money.
Or would I be better saving my $$$ for a Sundowner Solo with a back rest. With a sidecar I will never have anyone on the back of the bike so a solo is OK with me.