Lower finger holes
I find it puzzling that the lower holes veer off in the same direction on both pipes - to the left – on the lower pipe more sharply. One possible explanation occurred to me today: perhaps, the pipes might be switched around from my initial playing position (higher pipe in right hand), with the left hand taking the lower notes on the higher chanter, and the right hand taking the higher notes on the lower chanter. That way, another sonority system would become available, the holes would always slope ergonomically for the left hand, and the brain wouldn’t have to cope with switching hand positions – the right hand would still play the higher notes.
If we call the pipes H and L (High and Low) then, in this configuration, H would be played by the left hand in the 5th position (i.e. hand at the foot with the top 5 holes stopped with wax or pegs) and L would be played by the right hand in 1st position, allowing use of the thumb hole.
The main problem with this idea is the thumb-hole offsets. On both pipes, the offset is to the left, significantly more so on H. This would explain why, in my practising so far, I have had more trouble balancing H in my right hand than L in my left while exercising my thumbs. Perhaps H was always played by the left hand: this would explain the more significant offset of thumb and lower finger holes on that pipe.
I must practise for a few days to test out these ideas… What are the hole offsets like on other surviving pairs, like the Berlin aulos?