I bought the subframes for mine from larkspeed they are quick and reliable IIRC they cost about £100 each
the main advantage of buying the proper cobra subframes (as opposed to other brands) is they have mounting points on the subframes for seat belt pretensioners which means you can still use the seatbelts. Others such as sparco have no mounts and cannot be used with seatbelts
Although I don't use my focus on the road much driving on the road with harnesses is a pain so I have left the seatbelts in as well
the subframes bolt onto the seats and them bolt to the floor using the original mounting points the monaco s have holes in the bottom of the seats to base mount them to the frames the monaco pro can be side or base mounted with the proper subframes they bolt into the car in about 5 minutes
I have read a few posts complaining that the cobra mounts are too high and whilst they could be a bit lower I am fairly tall and havn't found them too bad
although a lot of people moan about the monaco being cheap and nasty I personally think they are good value for money and they are supportive enough on the track I have has a few incidents on track and they have been fine
al