I've used powergum on a helicopter rig when maggot fishing for big roach in has proved quite successful - v.similar set up to the one described here:
Lumbland: The Rig
The powergum cushions the hooklink to such a degree that big fish can be landed on very light hooklinks, I know Mick Dinnigan has landed 30lb + accidental carp using a very similar set up.
I'm not sure how effective it would be for chub though, personally I prefer to use 3-5ft of fluorocarbon behind the feeder and I'd be worried that the powergum would stand out a bit, and I certainly wouldn't use short-hook link for chub helicopter style. But it's always worth experimenting with these things.
Having been shown by Stef how to fish for Throop chub using a 2-3 inch, 3lb mono hooklength coming off the bottom of an inline maggot feeder, I soon learnt that on no account should you ever strike and that backwinding is essential!