Insoles and arch supports (esp. for aerobics)

[Judith L]

I've been searching and reading threads related to orthotics and aerobic shoes and still have a couple of questions.

Superfeet: Several people have recommended Superfeet footbeds and looking at pictures of it, I wonder:
1- How great is the arch support on these?
2- And whether the heels could be cut if need be, in order to make them narrower in the heels?

Spenco supports: I currently wear the hard Spenco ortho arch supports or Profoot's SuperSport arch supports. The problem I have with the Spencos is that the heels are rather wide for me and force the heels of my shoes to expand and they cannot be cut to be narrowed as the material is so hard. I'm interested in getting the Spenco Cross Trainer insoles and wonder if the heels could be cut in these and whether they offer any arch support?

Besides the Spenco Cross Trainer insoles does anyone have any other recommendations for insoles for doing aerobics?