2nd year visa forms for wwoofers/volunteers

I'm keen to start hosting Helpers this year (from Helpx) to kickstart the goals I have for this property (which are hard to accomplish when I have a baby in one arm most of the time), and a couple of people have asked me whether I can sign the 2nd year visa forms. I assumed that I couldn't, being non-commercial, but from all the reading I have been doing on it the past few days it seems to me that I CAN actually sign off on work, as long as:
volunteers are doing "specified work" (plant propagation, crop maintenance etc.... instead of cooking and cleaning, for instance)
volunteers work fulltime, 35-40 hours a week (which seems a LOT to me for no money, but maybe if I taught as much permaculture as I could it would be worth it?)
in a "specified postcode" (which I am)

Does anyone here have experience with the 2nd year visa forms? Am I missing something? Is it truly as simple as it sounds and I can indeed accept people working for their second year visa?
(If I am a non commercial operation and dont have an ABN, then their forms will have to be mailed in instead of lodged online but that is the only tricky part I have found so far)

looking for confirmation on this before I start telling potential helpers, "sure, I can sign off on that!"

any help/advice/validation please?

 

Depends on your postcode ,