hi i am running 3 door shell i have ordered a set of wheels team dynamics 8x17 and 9 x17 im looking to trim the steel lips and plastic arch out as far as poss i want to be right on the limit what is the lowest et i can get away with with arch heavy arch mods without stretch look tyres please any sound advise would be greatfully recieved especially if you have already trimmed arches back on your own car thanks bo