Currently I am using a Manfrotto panorama head, which is quite heavy and bulky a load to carry. I am therefore considering to buy a R1. On the website I found, that the +/- 90 degree shots are off the NPP. So I thought about some different setup. Could you please comment on whether this is at all realistic/possible? BTW I am using PTGui as a stitcher.

The 5D with the Canon 15 mm lens will cover nearly 180 degrees when rolled diagonally. So I am considering to mount the camera/lens diagonally in the R1. When the camera is then tilted upwards 7.5 degrees, there should no zenith shot be needed. It would then take 6 shots around. There should be an area of approximately 15 degrees missing in the Nadir. The nadir shot could then be taken with the -90 degree off NPP setting.

So, is there anyone, who has got some experience with a similar setup, or will this setup not work anyway? Thank you very much for comments on this.