Hello all. I have resisted requesting help here as there is so much fantastic information i felt it better to learn myself. However, i have come as far as i can along the learning curve and i would appreciate some advice. Ok, where to begin...

7d + NN5 + nadir adaptor + Tokina10-17.
Spherical panos.

Aim- successful indoor 360 panos to make vr tours and master the settings in a tricky environment for ease of use outdoors.

Work flow...
-6 shots @ 30deg + zenith + nadir + nadir patch using nadir adaptor swung to 180deg, tripod moved more than DPD in direction of front leg and re-leveled.
-ptgui pro
-mask tripod
-viewpoint correction on nadir patch
-extra targeted masking when necessary to reduce stitching errors in wide angle nadir shot & patch.

I have read and followed these links to find the optimal stitching position & nnp...
Tutorials: http://www.johnhpanos.com/tuts.htm
No parallax point: http://www.johnhpanos.com/epcalib.htm
Lower rail setting for optimal stitching position:
Entrance pupil database: http://wiki.panotools.org/Entrance_Pupil_Database

I found the LRS using the optimal stitching point tutorial above and confirmed this was in fact in line with the centre of my lens & nn5 rotator (about 57mm).

I have found the URS using 2 techniques (tape on the window with buildings in the background) and by setting up a vertical pole in my living room in line with a corner of the wall. In both vases i found to the LRS to be approximately 88mm which was lower than i expected. I tested settings lower and higher and using these techniques it kept coming back to about 88mm (cropped images attached). The mis alignments were more notable at +- 88.

My main problem is stitching errors in the bedroom where there are a lot of rectilinear patterns (book shelves, matt, doors etc). Primarily the stitching errors are most evident on the matt below the tripod, but only when the nadir patch is included. Annoyingly they are not consistent. I have tried to make panos with LRS=57 & URS with values between 86 & 100 and sometimes, confusingly, these did not effect the amount of stitching error, but sometimes its positioning along the edges of the matt. I cannot find consistency in the factors which may effect the stitching errors despite many hours trying and re-trying +- the optimal settings i found. In fact sometimes i got better results with non-optimal settings. Sometimes i got better results with settings i had previously used unsuccessfully. Sometimes the entire image would distort into a curve, but only with the nadir patch included. Of course my HDR attempts sometimes compounded the errors.

I have tried manually adding control points across the edges of the matt in the nadir & nadir patch, but confusingly, the stitching errors seemed to directly contradict these control points. Targeted masking has certainly helped reduce stitching errors, but it does not do so consistently, especially on either side of the tripod along the edge of the matt.

I read that the nnp in a fisheye lens is not stationary and is most affected at 90deg, i.e. the nadir. I wonder if this may be the problem but then everything i've read suggests optimum settings can be found.

I am ware that the room in which i am testing this is a challenging environment for panos but i figure if i can nail it here then i'm all set really. However, it is this complete lack of failure/success consistency across various settings which is head wrecking!

So, if you're still reading!...
Hints on work flow?
Suggestions on why i may be having trouble?
It would be great if anyone can suggest tried and tested LRS & URS for my camera / lens combo.
Are there circumstances when a decent stitch is simply not possible despite optimal calibration or can they normally be forced with clever masking & control points?
Is proximity to walls etc a factor?

Any advice or suggestions gratefully received coz i'm pretty much at a loss!

Thank you