i was told to use the 625 up front and the 7 on the rears as the rears will then have less braking

obviously the best peeps to ask would be the likes of mr airtec, ronnie amis, or mr brakes, martoon as they can offer real life real world experience of doing what you are trying to do

i had this set up on my 3 door and, to be honest, i wasn't impressed by the amount of pedal effort and after searching ages for a servo boost set up it was all just trouble as no one back then did an off the shelf item for a turbo'd engine