It's safe, but you will not feel the effects anywhere near as strong the second day. You'll probably have a higher chance of being still dissociated after the second day, because DXM/DXO have a fairly long duration of action. This means that you'll probably slur your speech more, have a hard time thinking etc on the seconfd day.
Dude, you've asked questions like this before multiple times. Don't use DXM multiple days in a row. It won't give you good effects. Just wait a week between doses at least.