Still getting a low efficiency

Just started my boil on the Nut Brown. My pre-boil efficiency came out to 64%, which is slightly better than the 60% I got on my first AG two weeks ago. At least this time I calculated the recipe for a 62% efficiency, so I'm hitting my numbers in that regard. My mash temp was lower than I expected even with preheating the MLT, putting my grain and MLT temp into Beersmith and hitting my water temp. Rested at about 148 when it should have been 154, I threw in an extra 1/2 gallon of hot water to bring it up, which it did, but I still lost 4 degrees over the 40 remaining min.
Anything else I could focus on to bring my efficiency up to the 70-80% range?

Unless your water ph is way off, I would look at your crush. The crush is the single biggest, and easiest, way to fix your problem.

+1 on checking your crush. My other sugestion would be check your spage temperature. I overheat my sparge water (to about 180) to make up for heat lost durring sparging.