John, your getting MORE recoil with your SLR's, as they are hand cocking only. The original semi spec rifles were more 'cussioned' because some of the gas was directed to drive the working parts system.
It would be a simple fix to fit new rivets to the 'T' mount on your top covers. I cannot remember without checking my own specimen. if the 'T' mount is steel or alloy. I THINK it was steel. In which case, a LIGHT run of MIG Weld down either side on the 'T' mount. Along the top cover mount webs, would secure it admirably! Job Done!