Mob Spawning Question

[Helliott]

Hello guys!
I've created this massive space underground in order to achieve optimal mob spawning.
I've added a thin layer of lava on the bottom of it and that successfully prevents mobs from spawning there.
However, my question is, does filling that space under my ground with walls has any impact on the spawn rates? or is it redundant with the lava already?

 

[CannedPotato]

If you are using a layer of lava at the bottom, that should prevent enemies from spawning on the floor already. Enemies underground (including bats) require the top part of a tile or platform to spawn, if the top (only checking the top) of the tile is obstructed by another tile or lava it will not spawn enemies. Since everywhere else below your bridge of stone is not a valid ground tile, enemies can not spawn there. No walls should be necessary.
I think that is an effective area for killing underground enemies. Make sure that you minimise enemies that spawn outside the box by not moving too far upwards or to the sides of the area, you can put markers down to indicate to yourself when to turn back so no spawns are lost.

 

[Helliott]

tyyy!, i will try to expand it a little bit vertically to add some jump area
It is a relief to know the walls aren't necessary because it would require some time lol