I've had Ural tubs completely disintegrate from rust. The worst areas are where the different body pieces are pressed and welded together.
I think you're better off just keeping the thing as clean as you can, though, and using wax- or grease-based products as a seal. Hard undercoating will chip away and then the chipped areas will trap moisture and promote rust. And the areas you would typically undercoat aren't the parts that get rusty anyway, not at first.
I've been keeping all fasteners and body welds covered with a thick clear military surplus grease, and anywhere I notice rust start to form I hit it with the stuff. So far, so good.
'14 Gear Up
'00 Bavarian Classic