So far in discussion of the Max 8 people have mentioned CFM LEAP cowling size and 737 tail design as possible factors in the need to develop a MCAS system to control tendency to pitch up at high AOA.
Since the tail has much more leverage than the wing (much longer lever arm), is it possible that the high bypass exhaust blast is affecting the tail at high AOA by pulling more downwash onto it by Coanda effect? At first I though the may be affecting the back of the wing, but then realized the 737 Max 8 is very close coupled (tail close to wing) and may be susceptible to stronger downwash effects.
I wanted to be sure before suggesting a larger horizontal stabilizer or considering lengthening the fuselage. Is it possible? Has it ever been seen before?