I’ve grown some seedlings using OFF-4 pollen, and the curious thing about OFF-4 is the high percentage of hollow seeds that it makes when used as a pollen parent. Lots of nice glossy black seeds…but a very large percentage of them are hollow inside. I dealt with this by making 3 times the number of crosses that I might normally make, and finally I got a fair number of good seeds. This year was the year that these seedlings would have bloomed , but they tend to be late-bloomers (later than plants using CC-3) and still had not opened when I traveled to the nursery this spring, so I did not get to see them. As you said, seedlings in general can have thick strong stems, but that does not always mean they will stay upright. The nature of their attachment to the crown seems to be the factor that makes the most difference.