I know I can never grow giant tomatoes in Hawaii. The biggest tomatoes and pumpkins grow where the summer days are very long. I can get tomatoes close to a pound but even Delicious which produced a Guinness record heavy tomato did not quite make a pound. The longest day here is barely 14 hours the shortest about 10 hours.
I had a friend who had been using the tomato set spray because he said his tomatoes never set. I asked and he was growing the tomatoes on a small strip of land between two multistory apartment buildings and the alley way did not get a lot of wind and only a couple of hours of light. So I told him, he did not need the spray, if he tapped the plant when it was in bloom to get it to drop pollen. No tooth brushes needed. I also told him there was probably not enough light if the plant only got sun for a couple of hours a day.
I noticed too, when the plant gets older and the leaves start dying, here mostly from fungal disease, the plant does keep trying to produce fruit, but the fruit does get smaller.