My crude but functional 1st hacked model: Rack Clip for @SMACKMAX  BUCKETS  so they won't fall out of the SMACKMAX STACKERS (Rack) 

No support, can print a lot on a bed. Clips on the rear of the bucket, with the lip facing FORWARD. They should stay in place, but you can glue them, and the bucket is still removable.

Quick & dirty, but they work! Thanks to @SMACKMAX for the cool buckets - you've used up several kilos of my filament!