If you go to Queensland Gas' Co half yearly report dated March 2007 regarding the Walloon Fairway(I'll try and paste the link below) page 13 , they are talking between 3 and 9.6m3. That means PES's 7.5m3 is right on the money. From what I understand its not all about the gas content its equally important how permeable the coals are so the gas will drain or vent out once the water table is lowered. That is what appears to be so good about the Walloon sub group coals, the gas flows and speeds up as time goes by.
Pes' Dingonose and Duckworth to the norht have higher contents at ave 10m3 and 14m3 ave..the later peaking at 17m3 which is way up there . Note these are due east of Sunshine Gas' recent announcement if you want to check that out.