A friend is looking at a older truck that is in very good shape but has rubber between frame and ibeam. My experience with rubber goes back about 40 years and a mack bought cheap. That thing was rough and swapped the rears for spring. Cheap truck now was expensive truck! Have these rubber blocks improved or are they as rough riding as I would remember? I think he should stay with leafsprings only as I do not trust rubber bags(another option) when dumping on weird grades, as most building lots are moving to hilly less desirable land. Gives the frame a workout backing around on these type of lots. I don't want him to get a xover road truck because these trucks are only good on black top or concrete. I see the term single but thicker frame. Are these as good as double frames? Trying to fill in the gaps of memory from past to help him!!