You can’t really tank T1 haulers much. If you’re concerned about that, you’ll kind of have to go T2.
As far as T1 haulers go, though, I believe the Iteron Mark V is still the one with the biggest cargo potential. I can get mine up to about 35k with T2 cargo extenders and T1 rigs. - But, of course, even with as much shield buffing as the 4 mid slots will allow, it’s still easily gankgable.
To get the best cargo space, you’ll want to look into freighters.