The difference between duds and fundamentally sound shares is that duds you have to sell at a loss if the price starts to go down. In fact it's perfectly OK to buy duds if you set an exit point before you buy. That is you decide I am getting in at 50, if it drops to 45 I am out or something like that. It's called stop loss. Having said that it's pretty silly to have bought LHCL at 105 or HVA at 70 or CSF at 20
Fundamentals on the other hand you can buy and hold through a downturn because they will sooner or later go back up.