None of the Klan robes in the aggy faculty/ alumni Klan robe collections belong to Sul Ross, as far as I know.
The Klan operated (operates) in secret. When Ross was “doing his thing,” his fellow white supremacists operated out in the open. That were that brazen.
The 1886 Texas election that brought Ross the governorship was so amazingly and so brazenly corrupt it set off an investigation by the U.S. Senate.
Racial cleansing of numerous counties, open lynchings, and when Black Texans objected, Ross sent state military forces to kill even more Blacks. The Jim Crow laws were first enacted under Ross.
Ross did everything in his power to openly support white supremacists from the Governor’s mansion. Since they knew the state would never prosecute racial hate crimes, and knowing a governor’s pardon would be given even if there was prosecution, Ross and his fellow white supremacists terrorized Black Texans without having to hide. (Remember the Jaybird-Woodpecker War?)
Hence, Ross had no need to hide his racial hatred behind a Klan robe.
After Ross' death, as the racial atrocities began to horrify more and more white Texans, the Klan flourished. And yes, during aggy home football games on campus, they did actually promote upcoming Klan rallies over the in-game public address system. Klan 48 was (is) the Brazos County Klan chapter.