It occurs to me there have been several recent accidents which involved using a gas mixture at an inappropriate time/depth. In theory, the decompression gases are the most risky gas you're dealing with (assuming bottom mix is normoxic or greater ). Considering these factors, it is my opinion that I want to see those bottles during a NOTOX [gas] switch. Placing highly enriched gases in a position that is out of view removes my ability to confirm the gas prior to sucking it down, and worse I'm now relying on a buddy almost completely for a gas swich. These ideas do not align with my approach to technical diving. Accordingly, I would encourage you to seek a qualified instructor and discourage you from assembling your kit in this manner.