eq2: I have read somewhere, don't/can't remember where, it was suggested that when using a Worm Inn, best would be to have lots of worms to digest the food with speed to allow frequent harvesting. I guess weight would have been the issue there too.

My concern about onion bags is durability. Once a spot starts to fray, the entire thing will come down into the barrel in no time.

Following your suggestion somewhere in another post (ahem), you could try this method and report a follow up here, Can't wait for it and thanks for experimenting.