Mounting the power supply underneath the board is something we recommend.
Why? Here are three reasons:
1) Mounting the power supply underneath the boards frees up more space for pedals on top of the board (and surely that is always a good thing).
2) You can place it as far away as possible from effects that are likely to cause hum, such as some wah pedals without having to alter your pedal layout (this is not an issues at all with DC7, CIOKS 4 or CIOKS 8).
3) Mounting the power supply underneath the board is a very effective way of protecting it if for instance someone decides to celebrate your presence on stage by dropping a beer onto your board. Or if you are playing an outdoor gig in rainy conditions*.
Unfortunately mounting the power supply beneath the board using Velcro is not always a good solution due to the weight of the actual unit. Some players get around this by using Dual Lock Velcro (which you can probably also use to tether a raging rhino) but due to the thickness of Dual Lock this option is not viable for players using super low-profile pedal boards such as the Nano series from Pedaltrain as the PSU will hit the ground. Traditionally this has meant that you then had a choice between zip-ties and screws (all CIOKS power supplies come with a drill template for this purpose). The zip-tie solution might work but it will not look very clean and while using screws is certainly a viable option for making sure the unit stays firmly attached to the underside of the board, not everyone is a fan of drilling holes in their expensive pedalboards.
We have come up with a solution for this which we call CIOKS GRIP. GRIP is basically a small metal clamp which you can attach to your DC7, ADAM or DC5 via the mounting holes and this allows you to mount the power supply securely underneath Pedaltrain boards simply by attaching the device and tightening two screws (which are included of course) without having to drill holes or use any other kind of tools. GRIP also allows you to move the PSU really easily if that is required