Be sure to follow all of Schroth's instructions/warnings.
The Rallye3 comes in two pieces- a rear "tail" and the front harness portion
we'll start w/ the tail piece first
the trim piece that surrounds the rear pillar where the upper seat belt receptacle needs to be removed
first remove the two phillip's screws that are visible
there is one remaining phillips screw it resides under a little tab in the front of the trim piece- this tab is in there tight- use a very fine tipped screw driver to pop it out- be careful as it would be easy to scratch the trim piece if not careful
the last screw revealed
there are two plastic fasteners at the top of the window- remove these (that fine head screw driver might come in handy again)
then carefully pop of the trim piece there are a few plastic pop fasteners holding it on
here is where the "tail" piece gets mounted- you can't get a socket on it (at least I couldn't)- it's 16mm- underneath a bolt head needs to be held (it's 14mm)- quarters are a little tight, but w/ a little work the nut/lock washer will come off.
there is a little trim piece surrounding the seat belt- it pops off easily to make room for the tail piece- mount the tail piece on top and snug the nut firmly
make sure the tail piece is orientated correctly (right side up) before bolting it up and putting the trim piece back on
insure the oe belt pulls out and retracts smoothly
for the front piece we'll be working at the rear of the seat, go ahead and push the seat forward
here's where we mount the right hand portion of the harness (the plastic cover snaps right off)- the bolt is 14mm- remove it
install the mount (again be sure the harness is orientated correctly and not twisted)
now to the left side- here's where we going w/ it
it's also 14mm- remove that bolt
this bolt has two spacer w/ a captive washer, it might not be necessary but I removed the washer and trimmed one of the spacers by 2mm (the width of the Schroth mount)- this was kind of a pita and may not be necessary but I wanted to insure there was enough thread engagement
all buttoned up- again insure everything is orientated correctly first- I had the oe belt twisted the first time, then discovered (after re-installing of course) that the left side harness was twisted as well!!!
congratulations it's not mounted you'll need to adjust the tail piece to your liking
the harness can be easily slid over the top of the seat and stored underneath the seat out of the way- not as handy as their Quick Fit- but they don't make a Quick Fit for 06+ Imprezas and have no plans to