24mph back half isnt out of the ordinary for a 10.00-10.30 ish car. A car as lite as yours I'd expect maybe 25-26mph, but your not out of the realm of reality at all. 27mph back half is a strong pulling car, or a bigger motor.When you see 27 mph on the back, its typically a 500" or larger motor. I'd say overall its pretty noraml, and not knowing your camshaft, gear and converter, I'd not be too concerned with it. Your incrementals show a failry consistent shift point. The 60' is a significant variance, but not knowing the track conditions, and weather, it may be nothing at all.