Mark, you are a more seasoned gardener than myself so take this for what its worth. You mentioned your fruit drop on your tree before, is that tree like the others in a semi potted/semi grounded type planting? Only thought is if its in a above ground pot, the feeder roots are possibly not large enough to support a big crop.
My trees that set a lot of fruit this year have been getting regular avo citrus food and I also did a single large dose of potassium sulfate and zinc sulfate to the trees early summer. That and watering hard and trees are holding onto fruit and look really nice.