Annoy all your friends! Lockdowns are not comfortable. They can also be used to stall and ruin a roll. However, I love the lockdown for the ability to whip down to recover the under-hook and also for electric chairs. Electric chairs are fun! See JRE 478 for the Bravo vs Gracie II breakdown.
There are several things I don’t like about the video below, but I wanted something that covered the whip up idea. An under-hook isn’t worth much if you’re flat on your back and far from the top player’s hips. The whip up is a movement to turn onto your right side and put yourself under your opponents hips where you have better leverage to attack sweeps. This was captured better in Mastering the Rubber Guard but I don’t have footage from that to link to.