Mount HDD on bottom of case like this?

[trueJack]

Any concern with mounting HDDs as shown? HDDs will only touch the case on one side and I will use rubber rings. To prevent wobble or vibration I will later add another bracket on top.

To clarify, there are two screws in the bottom. In the future, I will a bracket on top.

 

[sretalla]

Any concern with mounting HDDs as shown?

Yes, this:

HDDs will only touch the case on one side

but less of a problem if:

To prevent wobble or vibration I will later add another bracket on top

Seems you mostly thought it through... make sure airflow across the drive is sufficient (depends on where your fans are... can't see in that photo.

 

[trueJack]

The drives were cross-wise in the back of the cage. I thought I would create airflow from the bottom, but that did not pan out. For one, the PSU has to live there. I now put the drives length-wise so the air can flow around them from front to back. I will need to add a couple of brackets crosswise.

In conclusion, I am not quite happy with this setup. For one, I need to remove the PSU to replace drives in the back.

I have an order pending for a small HDD cage from China and I think I will put that in the back when it gets here, but it is taking forever.

Also, the cabling is a mess with so many SATA and power cables and I still have two drives coming. I will see if I can order some SATA data and power extension cables that work better.

 

[Etorix]

In conclusion, I am not quite happy with this setup.

This suggests you may want to look for a case that is designed to accommodate enough drives…
Your layout should be fine for cooling with some fans in front of the drives, but you still need to secure the drives at the top (vibrations!), wiring could indeed be problematic and replacing drives later on is bound to be a pain in the ***.