Andre's Re:
Slipping to the inside ,you would have to watch his right hand very close and have his rear right arm covered and or fully checked with your left.(their left isnt a worry as its already spent and over your shoulder,
and you would be even more open cross checking their left with yours.So it would pay to practice the next move into saftey while attacking ,Yes?

This following post of Andre's is from a different post, but I saw a few similarities:

For a very committed straight left:
What do you think about pulling your lead foot back behind your rear foot as you check their straight left with your rear right hand ?
(which gets you also out of reach ,specially if its a lunging shot), maintain contact with your right
and extend your right foot out to the outside of his left arm and attack over or under his left to suit his reaction to you going there, with either of your arms as you step in further as his left retracts,now your in south stance but up on the outerside of his left arm in saftey and you can attack with both arms but he cant until he moves.(of course you plan for that too and have him on the turn ).