Effy,
The symptoms of your harsh ride that you describe in your OP are unfortunately very typical of the F-53 chassis. Due to the heavy leaf spring suspension, you are only going to be able to do so much to try and soften the ride on the chassis. Obviously, sacrificing safety (i.e. too low of tires pressures) for what might only result in a slighty more comfortable ride should not be an option.
After you’re through getting your weight vs tire pressures resolved, you may consider a new set of high quality shocks. That will help with your ride. However, again, it’s only going to do so much. I know this all too well as my previous MH was on an F-53. I did everything that I could to try to improve the ride quality. Added front and rear track bars (to improve handling), new tires (weighed my axles and adjusted tire pressure accordingly) and installed new shocks all the way around. While these improvements did make a noticeable difference in ride and handling, in the end it was still a heavy duty leaf spring suspension.
Not trying to burst your bubble, just sharing my personal experience with a similar problem on the same platform.
I eventually solved the problem once and for all. I bought a DP! ;)