Blastomussa Wellsi Placement

[Steve2020]

Picked up this Blasto Wellsi yesterday and will be attaching to a rock in a few weeks. Question is, does the rock need to be fairly smooth or can it have multiple crevasses and still be able to spread over time? Do they spread up, down, sideways or all of the above? I ask because I would like to know where on the rock to place the Blasto.
Attached is the rock I was thinking of putting him on. Both front and side view. The white rock out of the tank is similar in shape and contour of the rock in the tank.
Appreciate any recommendations.

 

[revhtree]

Will you be removing them from the Frag plug? I wouldn’t and I would think that rock would be just fine.

 

[Steve2020]

Will you be removing them from the Frag plug? I wouldn’t and I would think that rock would be just fine.

I can keep the frag plug attached if you believe that would be the best thing to do. I think it would eventually cover the plug anyways. Would you mount hi or low on the rock? I am not sure if the spread towards light or away from light or if it evens matter.