"I tightened up my drag and then promptly lost them in both cases"

thats the deal there,have your drag adjusted before you fish,i've lost fish too tightening up my drag during the battle and have learned not to do it during,as long as the fish isnt going to spool you completely let it run! he/she will get tired eventually and you will be in here posting pics of your monster bass.I know its hard not to tighten down on that drag especially during the basses run but most drags will lock up /sieze if adjusted while the drag is running.
hope that helps,
tight lines(but not too tight in this case),
brian :7