[PyMOL] How to change the radius of only one loop without changing its position?

Hi, all,
I am trying to change the radius of one loop by making it as a new
object. But every time I do that, because the smooth-loop setting is
on, that loop just won't match its orignal position, i.e. connecting
to other part of the cartoon. I certainly can set  the smooth-loop
off, but it will make the figure ugly. Is there a better way to do
that?

Thanks.

Nian