As has been discussed many times on this forum and, as you point out,
asymetrcal constructions invite warpage. There are ways for asymetrical
constructions to work, depending on other factors as material selections.

I placed a six layer asymetrical construction on Steve's web site. If it not
still there, let me know and I'll send it too you as one example of what can
be done in lieu of balanced copper.

MoonMan

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