both should be in a separate cage for as LONG as it take for you to feel safe they can be introduced without fighting. A few days sounds short, we did scent swapping for 1 to 2 weeks and cage close together for at least 7 days. Even then I thought we rushed things alittle. BUT all our introductions went very well and very easy over all. seems like gliders like having company. our gliders ranged in different sizes, and that didnt seem to hurt anything, for introductions. in fact our colony of 7 has one malcontent, a very skinny female, she runs around giving chase to some of the others part of the night, we are trying to get her bonded to us, if that doesn't fix her aggressiveness she will have to be moved.
I don't think boy or girl second glider matters, just get male neutered.
Our females seem to go into heat, they want less to do with us and the males get all over them.