AIR 4.0 - IPA packaging slower with new packager

Here are the timings of our IPA packing:

AIR 3.9: 7:33

AIR 4.0, -useLegacyAOT yes: 7:41

AIR 4.0, -useLegacyAOT no: 10:35

As you can see, the "improved" packaging engine is much slower for us than the legacy packager - 10.5 minutes, vs 7.5 for legacy, ~40% slower.

This is on OS X 10.9.

Our main SWF is under 2MB, but we use numerous native extensions, and embed ~30MB worth of assets in the IPA as well.

Any help diagnosing or improving these incredibly long packaging times would be greatly appreciated.