How to change the collision polygon size or define other?

I'm using a small collision polygon to restrict the contact of one object with others. But in specific cases, would be better if I have a large one. So, I wonder if is possible to change the collision polygon area. I think would be better if there was more than one like happens with the image point.

Generally you use a second invisible sprite, pinned, to deal with this kind of thing.

Thanks, blackhornet

It seems a good solution. I'll give it a try.