I'm currently replacing the beams on my boat and when i put the striker back on i will be adding a tensioning device to it. There was little to no pretension on it b4 which is probably why my beam had cracked.
When rigged (i run a pretty tight rig) my front beam usually sagged up to 5mm and probably more whilst sailing.
Also where the strap bolts to the beam add a square/rectangular stainless washer that spans the width of your strap so the strap won't stretch and possibly break at the bolt.
i hope that answers your question Doug