I doubt it, the CS300 is 127 feet long... just about the same length as a 737-800. So a CS-500 stretch would probably take it out to about 138 feet or so... the same as a 900. The Max-10 is going to be a touch longer than 143 feet. So to compete against the 900/9Max seatwise would require such a stretch that I presume would limit the number of gates it could fit in. The 757-200 is 155ft, I don't know if they are gate limited or not. I do know that 900s seem to fit everywhere.