I would like some opinions as if anyone could notice replacing 100 feet of
rg-213 with 7/8 inch or larger hardline would be noticiable.

One ham said when he did he could tell the differance. I just don't see
that going from about .4 db or less of loss to .15 db of loss on 80 meters
is going to be noticed. That is about like going from 100 watts of
transmitted power to maybe 105 watts or less.

In the past I have inserted some 1 and 3 db pads in line with a receiver to
see if I could tell the differance and have a hard time telling that even
the 3 db pad makes much differance in casual operation, especially below 20
MHz.
Maybe some have more sensitive ears than I have.