Feeling of very large skybox in Unity and Oculus Rift

In our VR trainer scene created in Unity3d we have a vehicle and we are used real 360 degree panorama taken from one camera to create evironment inside a cabin.

Everything goes fine except feeling of gigantism of the environment in VR.

How i can avoid this effect?

This feelings came up only in headset, when i looked at the monitor surface everything looks fine...

screenshot:

IMHO it's because of the missing stereo information in your Skybox. The depicted room looks so narrow that in reality you would have differing views for each eye.

Projecting the image on a sphere instead doesn't solve that problem. A big enough sphere will look exactly like a skybox, a small sphere would provide stereo information, but still your texture doesn't, which will make it look like a flat wallpaper on a narrow sphere :)