You ALREADY have flowers opening? WOW! I'm no more than 40 miles or so north of you and my flowers have just yesterday erupted. I L-O-V-E sugar apples or I would have yanked them out years ago for more productive fruits to take their place,

Anyway, I stopped diddling with my sugar apples past where I can easily reach last year, and got about half as much fruit higher up where I cannot reach to pollinate as where I hand pollinated.

Both of my trees are fairly large now with approximately 2.5" and 3.5" trunks at ~9' tall. The smaller one so far always flowers first.

Regarding pulling petals, I read that pulling one is sufficient to give insects access. I pulled one petal off of every flower I pollinated to sort of mark which ones I already did.

The petal male / female cycle is counter intuitive, from what I've read when they have just opened they are receptive to the pollen and when fully open later in the day they discharge pollen. It's a wonder they survived all these past eons :-)

I have also tried defoliating them to see if they push new growth earlier but I cannot say they do. Good luck, keep us posted.