Hi. I could be wrong, but curled down leaves at leaf out on an October Glory is normal. I have the same initial phenomenon on mine. Wait a couple of weeks, or post a pic, so we can see, as it depends what you mean by curled down.
Many maples have curled down leaves initially - if you have seen a japonicum aconitifolium at initial leaf out you know what I mean, for example.
As regards the clay/amendment issue, a problem could occur if water is not draining well because of the different soils (amended soil versus surrounding soil), not the presence of clay per se. A good idea could be to raise the tree slightly above grade, make a rather large but not deep hole, etc, rather than amend the hole.

I meant to add, to clarify: This could keep the roots above the point where water stagnates - if that is actually a problem where you plant. I also assume you planted the tree at the very surface.
But, as I said, I don't think this curling down is necessarily a sign of trouble.

That's nice to hear.
Thanks for the opinion!
C_