Depends on ambient temps. Ive used a 600w hps with a 400w cmh in a 39x39 tent and could keep temps between 70 and 85 depending on how how much i closed my door.
IMO Simons method is over rated and i dont know where you came up with your %'s.
Most of the "pro" growers dont use hygrometers and probably dont even "cure" there weed.
If you try drying in tupperware i wouldnt leave it sealed for very long at all for probably atleast a week.
Id try paper bags or a cardboard box.
Any of these will make the buds more flat than if you hang them though