In my experience, this is related more to the stage amp and guitar you are using than to the POD itself. I play a HD500 through an DT25 and it is absolutely no problem to achive nice and controllable feedback with this combination. If you are going direct to a PA, it might be much more difficult. Remember: Feedback occurs only with certain frequencies, where the whole chain guitar body - pickup - POD - amp resonates. And of course, the guitar has to be near the amp for this wot work. My gut feeling is that the most important part is a good tube amp at the end.

I use a JTV, HD500 and FRFR monitor and have no problem getting controlled feedback at all - even at really low volumes: just have enough gain in the effect and amp chain!

As an example we do a few Pink Floyd songs and to be authentic I use the Highway amp model which is set clean, but also have a Colour Drive and Fuzz Face type distortions before the amp (rough copy of early Gilmour set-up).  With one or other of the distortions active you get distortions with quite different tones, but activate them both and the JTV simulated Strat gets into infinite feedback at the slightest provocation but in a nicely controlled way and as long as you are careful with damping unwanted strings can hold any note forever. 

It really does help that the JTV is effectively silent otherwise because otherwise this amount of gain wouldn't be practical without really heavy noise gate settings which would kill the effect obviously - do you use a noise gate in your patches?

with enough volume close to me I get all the sustain I want very easily