[Half Life]

Under Projection Properties in the MXED Texture Picker the Flip X or Y options do not have any effect.

[JDHill]

Do you mean Mirror X & Y? If so, these do not flip the image, they rather cause every other tile to be flipped (poor-man's seamless tiling), which means you'll see no effect when using Repeat values of 1.0 (because this math applies only within the context of UV space). If you want to flip the image for every tile, leave Mirror X & Y off, and use negative Repeat values.

[Half Life]

I guess I forgot what the mirror was meant to do, but thanks for the negative repeat tip, that gets the result I needed