Alan - yes, you are obviously using the tyres to absorb the bumps so tyre pressures will need to be soft, that is what you need to do, a very vintage method, but works of course up to a point.
However current practice with car technology, including Morgans, is to fit springs and dampers that are designed for the job of absorbing bumps & road surface irregularities and controllig roll then set tyre pressures for grip and handling - works too.
Have fun - PJB.
