R
rare breed
Try spring toggle bolts to hold the box onto the lath. you can push them between the lath turn them by 90 degrees or stick a piece of 3ply to the cleaned up lath if the plaster is thick enough and screw onto that. unless youfind the supporting frame location first and fix it to that. Re-aplying the plaster reduces the flex of the lath. each method has worked for me.