Problem matching image texture to displace modifier

I have InsaneBump plugin for GIMP, and it works great. I took a tileable oak floor texture and with GIMP/IsaneBump, it created a displace map (as well as a normal, height and spec maps). I used a mesh, subdivided quite a bit, UV projected (from top view) and mapped the texture. I did have to scale the texture to make the floor boards smaller. OK so far so good. Then I wanted to use the displace map made from that SAME image in GIMP, and use it with a displace modifier. I can get the geometry displaced OK, but it’s still at the original scale, so the image of the floor boards doesn’t match the bumps and cracks, etc. of the displaced mesh. I tried keeping everything at original scale first, and then scaling, but that only makes everything larger or smaller. I tried applying the scale first, but that didn’t change anything. Is there a way to keep things matching? I couldn’t find any reference in the user manual, or any tutorials.

It seems that if I change to “UV” in the modifier panel, it works.