pygame rect collision smaller than image

How can I define a rect collision detection smaller than image in pygame? I'd like to have a collision patter like the second image (link bellow), but I'm having a cut image when a try to set the width and height in the method rect.

When I try to set using image size, I have the collision detection in red

    self.rect = pygame.rect.Rect(location, self.image.get_size())

If I set the size using width and height, I just have the third image

    self.rect = pygame.rect.Rect(location, (32, 150))

I really wouldn't like to use pixel perfect collision, because is the slowest collision detection, so someone have some idea how can I achieve the second image collision approach using Rect?

http://ift.tt/1AuDj5u

Thank you!