How do you plant HC? I know you use tweezers, but what part do you plant?
The best way to plant HC is to take off 3-4 stems (preferably all connected together by a common root structure), and bury them deep into the substrate. You should only be able to see the crown and a few other leaves. The deep planting ensures that the plant will do two things: not float away, and root well to the new environment. With healthy roots, your HC should take off very quickly. Continue this method, planting each cluster of stems about 1.5-2.5 cm away from each other, or further apart if you don't mind waiting a little longer for a carpet to form.
This could potentially be back-breaking, but if you separate the HC into clusters of 3-4 stems BEFORE you start planting, you'll save yourself a lot of back pain by facilitating the planting process. Make sure you keep a spray bottle with you to keep the separated stems moist while you're breaking them up though!