I dont know about for screen printing but I would imagine the platens are close in size. I do
dtg printing and the platen that works for me is the long sleeve platen or pocket platen. I dont know if you use a pocket platen in screen printing but that is the one that works best for me with onsies. You are right about youth platens, they are a bit big for onesies expecially the smaller sizes such as 3 months. Hope this helps some

I dont know if it will since I am referring to sizes of
dtg platens but like I said they should be similar in size.