Backs are complicated things, and work best in a car when the vertical loading is reduced by spreading the weight load over an inclined plane - ie a reclined seat which will reduce stack load in your lower back vertebrae and the muscular effort of holding your trunk upright.
BUT modern Morgan trad seats are not designed to facilitate this. Yes, they recline, but for most body shapes they do not allow the broadest part of your back (at the level of your shoulder blades) to make full contact with the upper seat back, so the load you are placing on the seat is not spread.
I can bear 2 hours in mine before I have to pull over and stretch out my back, quite literally a right pain when my houses are 2.5 hours drive time apart. If my wife ever decides she wants to tour in the 4/4 new seats will be essential.
