Plus, the AA and LA lounges at SCL are nothing to write home about... I would clear out for sure.

Or, why not just take the 10:25AM flight from SCL to MDZ and get there earlier? MDZ is amazing and worth maximizing every moment possible!

We had the same situation (using miles) and LAN put us on the early flight with no issues at all. They were totally cool.

Also, sit on the LEFT side of the plane for AMAZING views as you fly over the Andes!