Easiest/Fastest way to move bathtub drain by 3 inches

I'm almost done with my masterbath renovation. Tiles, drywall, paint, all done. The next step is to drop in the bathtub. To my horror the drain is almost 3 inches from where it should be :eek:. I traced back the issue to inaccurate drawings provided by Duravit. You pay extra for a fancy bathtub and the drawing is way off but just on the drain position :wall:. I double-checked all dimensions when the bathtub was delivered and standing in my garage but the drain offset was a difficult one because of all the angles. I did not want to bring the tub through the stairs all the way to the 2nd floor for a test fit as the drawings looked accurate on all dimensions I could measure quickly with confidence. That was a mistake but what is done is done. I'm looking for suggestions on the easiest/fastest way to reposition the drain by ~ 3 inches. The new part of the drain is made of PVC and connects after the trap with a rubber clamp to the old ABS drain. I have ~1.4 inches of plywood on the floor under the bathtub (5/8 subfloor + additional 3/4 inch marine ply). On the other side of the floor, downstairs, we have the drywall ceiling of our dining room. That could be a pain to refinish nicely based on the natural light in that room and the open floor plan meaning that if one cannot feather in the paint nicely, one would have to repaint the ceiling on most of the 1st floor to make it look right. Hence, I'm leaning towards attacking the problem from the top and opening the floor. Is that the wise choice? How big of a hole do I need? Any better options? Thank you so much, Attachment 37453 (http://www.doityourself.com/forum/attachments/plumbing-piping/37453-easiest-fastest-way-move-bathtub-drain-3-inches-14-1.jpg)