Per DerbyDad03:
I don't think the posts or roll bars would prevent the skin of the roof from denting under
the concentrated weight of someone standing on the roof. They may prevent the cab
from collapsing and crushing the occupants in a rollover,

Mea Culpa: I had jumped to the conclusion that rollover survival was his
ultimate goal.

Now that you have said it, I guess there are reasons one would want to
stand on the roof - like sporting events or climbing on to a trailer or
something.
--
Pete Cresswell