Thought I'd update the story so far.
I've been able to give the 10mm XW a bit of a whirl. First light was in my 8" f/4 dobbie - by far the sharpest EP in my collection across the whole field. Very sweet to use.
Last night I was able to use it in my 17.5" dobbie. Seeing was the most stable I've seen for a very long time, AND it being summer too. Now, get this, the Trapezium in M42, A, B, C, D, E & F - well, yeah, BUT also
G, H & I!!! Pin sharp a ney a shimmer in the EP due to thermals. The number of stars that extended beyond these was sensational. Testament to the conditions, but the quality of the EP too. I had seen Trap. E & F before in the 17.5", but never this level of detail.
I did a sketch of M42 last night using the 17.5" scope which I've
posted in the DSO sketching sticky. It includes a close up of the Trapezium.
As for a 13mm or 14mm EP, I think I've found my silver lining in a sow's ear - my modified 13mm Hyperion! Last night it performed nearly on par with the Pentax! Not as sharp along the very edge, but it too was showing a flat field and pin point stars. It too was showing Trap. G & H, though I was more of a hint than definite - it really is faint- I used this modified 13mm to do M42 sketch. I think I'll give my hunt for a new 13mm/14mm a miss now. I'm very happy with this freakish mutilation of my sow's ear 13mm Hyperion,
Mental.