Joe wrote:

A couple of things don't seem quite right he there are commercial
trusses stacked up in the yards at all the box stores and lumber yards
and I have (so far) never seen any up to 30' or so with a bottom chord
bigger than a 2 x 4. Seems to me that a 2 x 8 is a huge overkill.

Standard roof trusses are designed to carry weight on the *roof*, not on
the bottom truss members.

Unless specifically engineered for it, the bottom truss members will
only be designed to handle the weight of the ceiling and insulation,
with enough extra to let people walk around up in the attic safely.

Chris