The rising producer of electric taxi aircraft has a lot of potential. The problem is the stock has already taken off.Archer Aviation (ACHR +2.46%) has given early investors a thrilling ride. The electric vertical takeoff and landing aircraft (eVTOL) company has seen its stock soar 264% over the past year, capturing the imagination of those betting on the future of urban air mobility. But after such a massive run-up, it's a question of asking: Is there still room for liftoff, or has the stock flown too far, ...