I wonder what could be so different in the design of the S9 and T9 that the T9 so much more inefficient 
The T9 has less chips and they run at a higher voltage internally to make up the hash rate. That is where you lose efficiency and gain stability.
Look at sidehacks S7 undervolt project for parallels. If you have enough mining boards available you can find s7 boards that will hash at .22 but the average board becomes very unstable at those voltage and clock speeds. The best I was able to get out of undervolted s7s on average was about .25 stable over the course of days and weeks. The S9s are similar in that bitmain sets the voltage on the chips as low as possible to hit the efficiency rating they claim but it causes major instability and premature failure of the hashing boards.
