I ended up with them 57" from the front wall, 44" from the side wall, and 75" apart. Listening position is 100". All measurements are from the centre of the THIEL name plate.
So I lost none of the soundstage width (which often goes wall-to-wall), gained some depth, and a little tighter focus in the vocals.
I'm somewhat amused by this, because it seemed to fly in the face of the wisdom of most literature recommending an 8' minimum distance between speakers. I've been able to free myself of the head in a vice behaviour, as a result.
I've been running through my usual test tracks and have been pleased with the results. Painter's tape markings have been repositioned accordingly.
My mileage has been varied...
Cheers,
Warren