First off most of the late elk seasons are private land only so if you have that option go for it. The antelope season Dec 5-9 is for youth only (12-17) and you have to have an unfilled tag from the regular season. Antelope has one season for rifle public the rest is private or youth.

Elk does have some late public land seasons but it is only in certain areas you just need to figure out what you can or can not do.

My advice is pick a area and scout the place out. CO has the highest elk population in the world you just need to be willing to do what it takes to bag one.

If you have a specific area in mind I might be able to give you some ideas.