The stays for the rear mount just in front of the gearbox mount infront of the strut tower on the left of the car and infront of the engine mount on the right of the car. Both finish via a hole cut oversize by 10mm, though the firewall, mounting opposite the side intrusion bar. These bars will angle toward the centre of the car to help with any flex/movement of the engine caused by hard corning. The energy in transferred into the cage which transfers it to the chassis rails. So the energy is not lost or used to unsettle the car.
With the front stays, they are finished under the dash, through the 'gutter' I guess you would call it( and a total pain to fit correctly..),then into the strut tower directly opposite the strut. Infact this is a total pain doing this job unless you sandblast the area as the glue is toxic, no room to work, very hard to prep correctly and balls of molten metal which cannot stick,'scar you'...
But if you can jump through all the hoops it can be done with no evidence that they are infact fitted to the car. The other option is to fit the 'bolt on' braces to the inner front gaurd which some people use. Im sure kam or evo will be able to enlighten us regarding these bolt ons.
Or you can seam weld the inner guard the fill with two pac high density foam which is just as good. Its light and very strong. Infact after the cage is fitted you could go crazy with the high density foam so its as stiff as a hardwood door!!