We only buy the Costco hothouse "cocktail" tomatoes these days: They are sold in a plastic package but are all still on the vine, and are like very large cherry tomatoes. All in the 1.25" to 1.75" diameter range. They actually taste like homegrown, right off the vine. I think the "completely-tasteless but easy to harvest and pack" tomato variety was perfected long before anybody could do GM. It was just selective breeding, same as practiced at the dawn of agriculture.

As for forming burger patties, I used to hand form them but I read a while back that they come out much better if you form them very gently. If you fry them, then you can make very loose patties just by moving the ground beef around without ever pressing it together to get rid of the voids. I guess it cooks more uniformly when the hot fat can bubble up through the patty. This does work very well when you have to fry or broil them.

For the grill, I do press them together just a bit especially around the circumference, so they don't fall apart. Another trick: Form a patty of uniform thickness, and then press down in the center with your thumb. This prevents them from bulging into spheres as they cook.