It's not too early...
I often pop them as soon as they are out of the egg. It only takes a second and isn't too stressful on them. This year I waited until everything had hatched before segregating them to their own containers, so some were roughly the age yours are now. The important thing is to do it before they get too old. After a couple of months, there's more tissue down there and it's harder to evert the hemipenes. As for how old is too old, I don't know, I've never waited that long. But I have made some sales later in the year and it was harder to prove gender than on tiny ones. I'd go for it. Be quick and gentle, they usually don't even seem to notice.