Do you have any idea why the model appears so small relative to the HDRI? No matter what I do or select, I can't seem to scale the HDRI down. Right now, the house looks like it’s sitting on the ground, but it’s only about the size of a human palm compared to the HDRI. I’ve tried using several different HDRIs, but the result is the same for all of them.
A spherical HDRI is captured from a specific camera position, so the apparent size and perspective of objects are baked into the image which is projected onto an infinitely distant environment dome.
Because the environment is treated as infinitely far away, zooming or scaling the dome will not change the apparent size of objects within it. A real solution would be to use an HDRI captured from a greater distance.
This is also why HDR sky environments with no buildings or other elements close to the camera usually work best.
You can also try using the Finite Dome option in V-Ray’s dome light.
Enable the Finite Dome checkbox and increase the radius and projection height.
This doesn’t work equally good for all HDRs but it could help.
Konstantin