We did that in one of our orchards up north years ago when we wanted to convert to high density planting.
We ran into compatibly issues with the Antonovka overtaking the 27.

Thanks for the info. But I'm wondering...what exactly happens? Does the Antonovka send out suckers, or does it reject the graft, or what?

kokopelli5a I think this is just one of those things that sounds like such a good idea except for one little thing. Thank goodness turtleman49 happened by to save you all the wasted time and effort of finding it out for yourself. Good follow up question though. I would like to hear what the answer too.

You just end up with union incompatibility. The structure of the Antonovka will over grow the 27, so what you end up with is a trunk that is larger than the scion. In our case it ended up with a trunk around 4" and the 27 at around 1",, It made a really neat looking burl though..
We had already inter-planted the rest of the orchard so we just pushed the Antonovka out and replanted.