It's more a matter of height, not load. There is no roof rack, and he will be running stock for some time. It's just nice to have a bit of the extra clearance and to be able to run larger tires since he will be doing some trails in the coming years.
I've always run MD on my Disco's, both I and II series. They do sag a bit once you get loaded for a weekend camping. But this will be a single high schooler's truck for at least the next two years.
The tires that were on the truck were so bad I was afraid to drive on them in the wet, or at freeway speeds. So if I'm going to spend $1000 on new tires, I wanted to get 235's or so, which means the lift is needed, thus the hunt for a set of 'cheap' springs. But since I got a nice set of Duratracs for "free", I am sticking with stock size, and height for now.