My experience is that the HC I planted in individual pieces is doing much better than the clumps I planted.
Tho the clumps survived and appear to be growing, they were an algae catcher and still have a little BBA which I'm working on to remove.
On the other hand, the single pieces which were stuck down deep with a long tweezer, appear to be spreading nicely close to the ground.
Note about Flourite: I used Flourite Dark, which apparently is even bigger than regular Flourite. Had I realized this at the start I would have put down a smaller substrate.
Note about light intensity: When I first started my hung lights were a little too high for the HC, I kept lowering the lights a little at a time until I could see the HC responding.
I'm also adding pressurized Co2 to replace my current DIY yeast.