I am one who's stated here that leaves in proximity of the fruit are the key contributors to the fruit's sugar, but it seems things are a bit more complicated than that.

Annual pruning performed on apples in mid summer has consistently reduced brix somewhat (not more than about a point) for the fruit, even without the removal of wood near fruit- I'm really unclear about the reasons. Remaining leaves should have been better lit including leaves near fruit.

I do know that carbos are supposed to be transported by gravity and not capillary pull so lower leaves cannot sweeten higher fruit.

If I was you, I wouldn't leave any part of the canopy that wasn't well lit and seek to have even light distribution throughout the tree. That's pretty much how I prune these days anyway. Most of my plums are being converted to open center this year for this reason. I believe in doing this once trees are pretty well established.

If your trees can't be managed like this this season you might as well just thin all the shaded fruit unless you have some use for it. I'm guessing that you don't even like sharing anything but your best fruit.

Optimizing fruit quality is a priority for me, but not the primary part of my plan. Because extending the harvest of high-quality fruits is more of a priority, I thin upper and lower regions equally. Most times the lower fruit ripens a bit later than fruit at the top of the tree (I assume this is because bloom set tends to happen at the top first). At the end of the day, I am unable to quantify by taste if the lower fruits are actually less sweet. Most fruits become sweeter by just letting them sit longer on the tree, regardless of location on the tree.

Thanks for the comments. I should probably just prune out that lower apricot wood where I know from past experience that the fruit quality suffers. Tasty Rich is my earliest apricot, about 10-14 days ahead of Tomcot. I remember last year the last Tasty Rich fruit came off after Tomcot started. That 16 brix lower Tasty Rich didn't compare well with upper 21-22 brix Tomcot.

Think I'll leave the lower wood and thin the fruit hard. Try to see if with enough thinning that lower fruit will mature sooner and with higher quality.

Spread mylar on the floor around each tree. Shouldn't be too hard to keep down inside a green house. I use side reflectors on the overhead light set up when starting seeds inside.

ace:

Mylar would probably be great. I do have an issue with holding the ground cover in place but only when cleaning up leaves. Sometimes I use a leaf blower. I've been using a white reflective material as a ground cover since 2005. It's woven like weed barrier and can be pinned down.

I would leave the lowers and use them for preserves where you're adding sugar so the brix of the fruit doesn't matter as much. Or take them to a homeless shelter or food pantry.

I would only avoid growing them if doing so helped the other fruit on the tree.

My experience is similar. That is, the lower interior fruit is smaller and less sweet, as is industry recognized. Interior fruit also harvest later, but even leaving them on the tree doesn't improve the quality enough for me. This year I plan to completely remove them from the tree.

As mentioned, I'm sure it depends somewhat on how aggressively trees are pruned.