You ask there for you shall recieve.
The front going across is 8 5/8", the back going across is 9 3/8" and going from front to back is 10 3/4". The front mounts that bolt to the seat are at an angle so keep that in mind. These measurements are from the seat bracket to the seat and they appear to be square to each other.
Measurements from seat bracket/sliders to the body are 17 13/16" front going across 17" on buckle side going front to back 15 5/16" going front to back on the outer side(airbag side) 19" rear going across. These measurements are hard to measure since the holes are not square to each other since the front mounts are directly in front of the sliders and the rear mounts are on the inside and outside of the sliders. On the plus side at least these holes are flat and not angled to fit the body.
It sounds like you may be able to make brackets to bolt the existing focus seat brackets to the suede seats but keep in mind that you will loose the airbags in your stock seats and if you are not using the stock seat brackets you will also loose the seat belt pretensioners, any of these not being used will cause the airbag light to illuminate if that matters to you, just thought you should know that if you didnt allready.
The only way i was able to get these measurements are because i have a set of the EAP recaros in my bedroom right now that im getting ready to install as long as i can unbolt the stock brackets and use my brackets that are in my car right now since the brackets are FUBARed from shipping.
Good luck and keep us updated.