The PP is nothing but an exercise in frustration.  Aside from the low per image payout, the concern that you're cannibalizing your own sales, the poor connector between the sites, the reporting problems, the lack of credit, the fact you get no RCs for sales ...

Sorry, what was your question?

I did exactly that - moved some "dead wood" over, about one third of my portfolio - and in my experience, it makes less than 5% of my monthly royalties compared to normal iStock sales.  Of course, as poor sellers on iStock, I guess it's hardly surprising they don't sell much on the PP either. 

Others seem to be doing better, but perhaps they move across everything they can.  Your mileage may vary!

And all the things that Sean says are true...