How can I retain masks when flattening layers?

[Hank Alspach]

My client would like the layers flattened on the artwork I create. Most of the time, I put masks on their own layer above the layer containing the masked objects. When flattening artwork created this way, Illustrator turns off the mask, ruining the artwork. Is there any way around this besides putting masks and masked objects on one layer? (I understand that a mask will stay intact that way).
Thanks!

[Gary Newman]

Well, the paradigm for Illustrator 10 is that every object is on its own layer, and flattening removes masks because objects in other layers ore merged into the same layer as the clipping path. The exception to this is groups, whcih will not be broken by flattening. So if you must flatten, make your masks with groups by constructing them in the AI8 fashion. Put the clipping path on top, select it and all the objects below it you wish to clip, and Command - 7 (Clipping Mask - Make).

[Hank Alspach]

Thanks, Gary.
That is essentially what I'm doing, though. Within AI 8, I'm grabbing those elements, with the mask being on its own layer above, and selecting Masks>Make. This creates a "group", correct?

Flattening everything then removes the mask, regardless of the stacking order.

[Gary Newman]

Illustrator 8 allowed masks to work across layers, so a mask could be in one layer and clip the art in other layers. You could put an object inside the mask by just dragging its layer between the masked layers. When you flatten the artwork, you lose the mask. You can resurrect your flattened maks by selecting the same group of objects, including the clipping path on top, and hitting Command -7 again.

[Hank Alspach]

I assume then that it's best to group things before I apply the mask the first time? (so that it's easier later to grab what you need and re-enable the mask)

Ironically, when you backsave to Illustrator 3 or 4 format, the layers are discarded but every mask remains intact. The downside is that all gradients are converted to blends.