Hide the bodies so only the shell model of the subframe closest to the flexure mount is showing.
Insert a new Manual Contact Region. Right Click on Connections, Insert>Manual Contact Region.
For this contact, you will want to select the four faces of the shell geometry (Face Sheet Surface_100mm holes) and apply it as the target body (Red). Then select the flexure mount surface near it and apply it as the contact bodies (blue). You should be able to select it through the shell model.
Repeat for the remaining seven flexure mount and center subframe connections.