Sometimes when exporting a displacement blend texture, the scale is incorrect in Hammer and Source. This happens even with the current default blend texture that Wall Worm applies to displacements.

This problem occurs when you are not using the same texture dimensions for both the materials in your blend material. Because the scale of faces is partially detemined by the dimensions of the bitmap on a face, the scaling is determined by only one of the bitmap dimensions; when the dimensions are not equal, you can have unintended results.

For example, if the diffuse bitmap in Material 1 is 1024x1024 and the diffuse bitmap in Material 2 is 512x512, you will not always get the scaling you expect. Try to use bitmaps of the same dimension.

If you need to use bitmaps of differing dimensions, you can swap materials 1 and 2 in the blend material before exporting the VMF and see if the scaling is now what you intend.