If the plant is sparse, it's probably not healthy. It's not the plant's nature to be robust and display sparse foliage at the same time.

Maximize branch ramification by pruning all branches with 4 or more leaves back to 2 leaves. Get the plant into full sun. Make sure your soil drains freely so you can water profusely every time you water and feed weekly at 1/2 strength through Sep. I would suggest any fertilizer with a 3:1:2 ratio, like 24-8-16, 12-4-8, or 9-3-6. I can tell you now though, that unless you keep branch length under control and the canopy open so light can penetrate, you'll have lots of trouble maintaining much in the way of interior growth.

Al

maybe by me saying sparse was miss leading. it is not sparse and is healthy, just not as fully as i would like. many yeas ago i had one that was very dense and would like to get the same effect now.

You will get maximum branch density (ramification) if you follow the instructions directing you to cut all branches back to 2 leaves as soon as they get the 4th or 5th leaf. This removes the apical meristem from a woody branch, and it will grow 2 new branches from the remaining 2 leaf axils. This keeps growth very dense, and provides you with myriad pruning opportunities, allowing you to leave the branches that compliment the tree's form and remove those that detract from it. Benjaminas (all Ficus) will fill in very quickly when managed this way.

Al