To see where the 1/2 way mark is lay your machine on it's back and look up into the area where the needle shaft goes into the machine. It should be where the pressure foot lever raises and lowers. You just have to move the pressure foot lever towards it when you lower it.
I have the 7570 and I put just a bit of pressure towards the back of the machine on the pressure foot lever and it catches the 'hook'.
Good luck!