Depends on your tanks, both AL and Steel. Most of the rental Al80's I happen to run into are Catalina at 1.6-1.8 negative full. I own Worthington (XSScuba) X7-100 Steels, which are 10 negative full (*ASSUMING* you get a full 3442psi fill!. You will often get a 3000psi fill on your own HP100's, either a hot fill, or they may not have the mobile compressor on the liveaboard to do 3442). That brings the difference down to approx. 7.2lbs.
I recently dropped 7lbs, using my steels on trip with PCB Dive Charters (who gave me solid 3500psi fills on all the dives... thanks Kyle!), and the weighting felt pretty good -- probably could have dropped another lb. without issue.
I recently dropped 7lbs, using my steels on trip with PCB Dive Charters (who gave me solid 3500psi fills on all the dives... thanks Kyle!), and the weighting felt pretty good -- probably could have dropped another lb. without issue.