I actually got to fly an LT-40 with an OS .52 4-banger in the nose, one of my student's planes. Great flying plane, plenty of power. It actualy felt better in the air than the ones with the .46 two-strokes. I'd say the LT-40 is a natural fit to the .52.

However, your comment about wanting it for acrobatic planes later makes me agree that the .72 is probibly your better bet.