I dont find speed on the flat translates to the hills at all. Climbing, particularly long, steep climbs, are a complete different beast, IMO, and need to be practiced. Its almost as much of a mental game as it is a physical one.
The extra weight won't help, and will probably be more of a burden on long climbs than it will on the flats. 10lbs is more than half a bike extra weight you're carrying.