Premollar Extraction to Fix Overjet?

I am in braces and am an adult, but still have a 10% overbite and 4-5 mm overjet. I have been wearing elastics. My orthodontist said elastics will not correct the overjet any further because I am missing a bottom incisor. He said the only way is to pull 2 premolars on top. An implant for the bottom tooth is not an option. A dentist acquaintance advised against pulling as it would make upper lip too small. Will this make my lips look smaller, face sink in, mouth feel too small, cause TMJ?