If more travel to the inside is essential it might be possible to grind the body of the front derailleur where the inner limit screw strikes so that there is less metal and the screw can be backed out even further, allowing the cage to move just a little further before hitting a stop. Might be worth a try. I have not looked at my Mountech to see if this is possible but I have done it on a different derailleur.
'Net photo.
