Yes it is very often weight restricted and many S/A's don't get on. We have a cargo contract that pays better than coach seats so sometimes you see empty seats because cargo being protected. Sometimes we have a backlog of cargo. I'd say with 80 open you are ok as I've never seen that many protected. Has gotten a little better with the 777-300 added. But each day is different...might be just fine or perhaps no S/A's get on for a couple days. Have a back up.