I don't have any experience hatching eggs in a special egg tray. You may want to post in the Incubating and Hatching eggs section for some more answers:Incubating & Hatching Eggs
Glad you could join the flock! Yes you can hatch in cut down egg cartons. I use this method all the time, I started out using it because of shipped eggs and damaged air sacs. Liked it so much I do it with all eggs now. I can monitor eggs progress with out losing track because of hatched chicks knocking them around. The only down side is that you can't see a wrong end pip in eggs. But I'm a hands off hatcher and dont interfere and wouldn't look untill hatch is complete anyway. I use new cut down cartons to hatch in, cutting them down so they are shallow but still enough to support the egg. Cartons make clean up a little easier too.
These are just my own thoughts on egg cartons definatly post in the incubating and hatching section for other members experiences as this method is not everyone's cup of T.
Wishing you the best of luck and hope you enjoy BYC