EvilGN,

If you have the 1500TT as well as the other ATP requirements (FAR pt.61), you would most likely be eligible for upgrade before you even finish FO training.

However, your plan sounds good. Get enough months in the FO seat until YOU feel comfortable with the upgrade. Just keep an eye on hiring trends/upgrade movement so you won't miss your window of opportunity.

Good luck with the application/interview process!