What is your reason for just wanting to lower the rear? I can tell you for one it is going to look like you got a bunch of stuff in the hatch, and will most definitely adversely affect the way the car handles due to the fact that most aftermarket springs come with a different spring rate and most likely would not be the same as the fronts on the ST. I had a 2005 base model Pontiac Vibe that I lowered all the way around with Tein S-tech springs... 2 in drop... Mainly just to close up the ugly wheel well gap (which the ST has no such issue) I didn't even think it would be noticeable till I got in it after I was done and could immediately tell it was lower... I also installed Tokico struts along with the springs... I loved the way it looked and it handled like a dream... but my overall daily drive ride quality took a major hit... bouncy on straight roads and rough pavement and curbs were my enemy. As far as the ST suspension.. I don't think there is any reason to modify it... Ford went through a great deal to design this car and from what I have read all over the internet.. out of all the "Hot hatches"... The ST's suspension came highly praised... especially in Europe. So unless you are doing a total appearance overhaul or going to race on dirt.. I would leave it as is... I also forgot to mention that having my Vibe lowered those 2 inches caused the tires to rub and wear massive holes in my fender well covers along with a battered and bruised front bumper cover... parking blocks will show no mercy... Best wishes!!
Glad I could help!!! I see you own a blue ST as well!! Actually when I went in to buy mine... It was the last day of the 0% for 72 months financing and I went to the dealership only wanting Silver(my first choice), white, or black... I told them maybe red... but def not yellow or blue... well after 5 hours of the dealer drama... they were able to locate a black or blue one... so I told them to go for black and then they got a call saying that they had to disclose the fact that the black one I wanted to get had the sun-roof left open and was rained in... so I now own a Performance Blue ST 1. I love the color now.. As far as mods... I see your retired... and unless your some sort of internet tycoon or something and you retired at 35 (and would most likely not be driving a Focus)... I would be modest with your upgrades.. So far the only mod I have done is installed a Green air filter... I bought a Boomba rear motor mount... but decided not to install it as I have read numerous posts about aftermarket mounts causing bad vibrations and even causing cylinder misfire codes... I'm not doing anything until my warranty is up... and that is my advice to EVERYONE!!!
I had a performance blue 2012 focus sel with 6speed automanual trans.I loved the car hated the transmission. I told the dealer all I wanted was the base ST mainly for the transmission in blue preferably. About a week after leaving the dealer they called me something I'm going to really like. So my wife and I go to see what it was. It was a Tangerine Scream ST3 fully loaded,nice car but at just under $32,000 told him not even close to what I wanted. Finally decided to just order a 2015 with just what I wanted which was really no options. I kept building 2014 at the Ford website then look up the vin number to find where there were located. I also got good coupons from Ford. When the coupons were about to expire at the end of the month, I found one at a dealership about 30 miles away. I told my wife lets just go look at it. They had the car read for a test drive. Long story short, we were on our our way home in an hour or two. With dealer incentives and a couple thousand in coupons we saved about $8000 we're completely satisfied and ready to make some subtle modifications