When I spoke to Margaret Callaghan (sp? good Melb LC) she said that in her opinion, and contrary to what some others will say, that nipple shields reduce the milk going through by 30% - she doesn't see them as helpful to milk production or for baby.

Have you thought about seeing an LC so hopefully attachment will be okay from the start and you wont have any attachment issues / nipple problems?
I second that! I am also surprised that the person you spoke with from ABA told you what sort to get. I mean don't get me wrong nipple shields do have there place but you really need to try all other options first. ABA has a policy about recomending Nipple shields & it is that they be used as a last resort.

I think you should get incontact with an LC or if you like I can find out of an ABA counsellor who is experienced with inverted nipples to help. There are lots of things you can do to help your baby attach.
For example sometimes expressing a little before trying to attach can help draw the nipple out to make it easier for baby to attach.

This may be TMI so don't feel the need to answer it on here but think about it. A truely inverted nipple doesn't become erect when cold/stimulated. Do your nipples ever poke out? If they do then you should be able to master bfing without a nipple shield. It just takes the right support to get you there.