To find a T-Pose, it is best to use MotionBuilder. Put all the bones in position 0,0,0, and adjust the angles, which must be equal (like a mirror split in half...), both in the X,Y,Z coordinates... Save the Fbx in "Python tools" menu in version 2013/2014/15, and import Daz as "Pose".
Normally, you can use the "DazToMaya" script, which is not updated for G9, or directly, a "normal" fbx in MoBu. There you tweak the angles in all the orthogonal "views": They must be completely straight to the origin.
But, try "my" g9 T-Pose... https://www.mediafire.com/file/90knq9iqybupqt9/g9.fbx/file
And, save as "pose"... 🙂