I don't have a tach on my 05 WG, but all V-Twin engines like to be up in a "happy" rev zone, keeps the oil pressure up to the heads, etc. Just ride by the "seat of the pants" feel, where the engine sounds happy.
I can tell you that I always have 2 nd. gear at over 20 mph, 3 rd. gear over 30 mph, 4 th. gear over 40 mph, and 5 th. gear over 50 mph. Below that and my bike starts to buzz & feel sloppy.
2012 Heritage Softail Classic, profile laced wheels, security, ABS, two tone color - Ember Red Sunglo / Merlot.