You have a very interesting case here. You have measured the tops of the pistons and confirmed that each one is properly reaching the top of its stroke. This rules out the possibility of a bent connecting rod. Of course, it might be possible that the rod has bent in the last 10K miles, but, the oil consumption was quite high prior to removal of the head and it has not been reduced since the replacement of the head gasket.

When the head was off the vehicle, was there any replacement of valve guides or valve seals? Were these items in acceptable condition?

Is there any possibility of the turbo consuming an excessive amount of oil? Maybe you can pull the intake and see if it is flooded with oil in there.

What about blowby? Maybe you can disconnect the hose from the valve cover to the intake and run it into a bucket, underneath the hood, for awhile and see how much oil is getting sent to the intake. You would need to be able to drive the vehicle in this conditon to get any useful information. The bucket would need to be secured in some fashion down near the bottom of the block.

If none of these items appear to be the culprit, then it is possible that the oil is getting past the rings and being burnt in the combustion chambers, however, I would think that this scenario is the least likely of them all.