The size varies a lot. Some vines will never make fruit bigger than a golf ball, while a different vine could produce fruit as big as baseballs, or anything in between. The fruit usually reaches full size quickly, maybe in two weeks?, so yours may be as big as they will ever get. They will feel hollow at first, but as the seeds and arils grow and develop, the fruits will get heavier. From bloom to ripe fruit varies, but a good ballpark figure is about 8 weeks.

Thanks. Will they change color? I was told to let them fall off on their own.

Some turn yellow, some don't. You do want to let them drop off. You can store the fruit in a cool dry place for a few days until it shrivels a little bit to reach peak flavor, if you want to see how one tastes. Some are good, some are bad, most fall somewhere in between.

The first one was pollinated on 6/15 but still feels hollow. The others were pollinated around a week later so I've got approx. another month to wait. I would like to taste one but I'm not growing them for the fruit. I would like to get some viable seeds for a couple friends though. If that fails I will just root more cuttings or dig some roots come next spring. I'll probably take cuttings to overwinter anyway just to make sure I have plants next year. Thanks again!

Well it was hardly worth the effort involved to eat what little was there on the first fruit but it was tasty. The others are a bit bigger so they may contain more meat but probably just more seeds. We'll see when they drop.