The attic stocks r80-r99 items, has a chance to stock every 7 minutes on the second 51
You can currently get only 5 items a day from the attic, TNT changed that to prevent abuse from ABers
To check the times, you can go here:
(you need an account to see links)
(not sure if this works anymore)
and here for the full time chart:
(you need an account to see links)
For the ABer settings, since there is no haggle (it's click and buy), a buy time of... 100-300ms for example is considered safe.
Just don't run for too many hours straight and take same precautions as regular ABing such as using a proxy and stuff ^^