Black locust is very sensitive to variations in the spring seasons. Locally, it has only bloomed sporadically in the last few radical seasons. 25 years ago, when seasons were consistent and predictable, we had good bloom every year, but we didn't get BL in the supers. It bloomed in the lull, just before the "main flow."
I think I know how to get locust honey in the supers in that circumstance. Not my idea, but was told to me by an east TN beekeeper. Looked for him for two days at the conference to get his name to give him credit for the scheme, should I report it later.
Goes like this:
Prior to BL bloom, put all the frames of brood of a double deep in the upper box - wall to wall brood.
Place all frames of stores in the lower deep, making sure that the brood above was not separated from the stores below.
Transport to the BL area.
Add two supers of drawn comb at the top of the double deep, without excluder.
Seems to me that this technique would be effective for any varietal honey. The bees "want" to add liquid feed immediately above the brood - standard procedure.
Walt