Is the option even viable? I have a monokey universal plate for top box mounting on a rack. I'll be wanting to add some hard saddlebags, small ones, to the bike and wondered if these plastic plates, mounted to a steel/aluminum frame to the bike, would be strong enough to hold them. Nothing too heavy, just clothes. I see them list the rectangular tube frames for side cases but not these. I believe the monokey cases all use the same fixing points so, any opinions? Thanks.