BPH,
Would you mind providing a link with details of this extension arm you mention.
As you may have read above, I mount on the px side yoke in the C172. I did try positioning the arm under the yoke but it was not long enough. I do remember at the time I tired thinking that it would have worked fine on the P1 side if the arm had been longer.
I think I have a similar seating position and sit with the seat elevated, despite being 6ft.
I did not know extension arms were available.
Thanks.