Can't really say I have found them much different to a defender as regards the impact on your body.
When I was on forestry work in the 80s and 90s we had several Series on the firm, driven on the roads, but also fields, and lots of forestry tracks.
I still had a 109" when I got my own farm (heavy clay, saturated in winter), and used the 109 on and off the farm for about 8 years.
Then had a Ninety, which I used on the farm, on the road, and for quite a few laning trips.
The Ninety was maybe a bit softer ride than the Series, but maybe bouncier. But not much in it really.
Reckon you are just a bit of a Wuss if you can't drive Series!