3- 4 feet, even etoliated, should be a decent brew. At least I've heard- never brewed PC before personally.
It looks like the plant is not etoliated where the box light is, so you might want to cut it and root the cuttings whenever it gets taller than the lights. The log style rooting does work, and with your situation, pups at the soil level would be ideal. You just cut it into smaller pieces and plant them half out of the soil, root side down in this case.
How often do you water that plant? The part by the light looks like it might be a little dehydrated, though it's hard to see in these pics, which would also contribute to aerial roots.