Scott
3rd party racks do work, but as you indicated , it’s a tight fit, especially in the context of a door set, aka for the back.
You can follow for all Gen6 the same process as HD400 with exception to A2000, aka using Dell-EMC TitanD racks.
In regards to the A2000 ( read 40in deep), you can use APC 3350 or Dell-EMC Titan HD. In all 3 scenarios, the equipment can be supplied by your DELL-EMC team.
Reach out to your Isilon SE for details.
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