i am just a beginner in terms of VRay,
but there's one trick i use to align the horizon of the backgroung (see image below)
it's not perfect because it only stretches the image, but sometimes it works
you can stretch it in height or width... in this example i needed it to be 87% height stretch so the horizon was where i wanted
1.jpg
but yeah, this is one of the things that is missing in VRay4Skp
this and a vray material picker