Having been out for a run the other day I checked two things.

No space to turn the roller without it fouling the side wall carpet.
The whole arm would have to be turned as well which would negate half of the sideways movement.
I find it very comfortable as is.

I could not imagine where I could put a foot rest above the Clutch Peddle on the Roadster as the Peddle sits quite a way forward and would require bending my knee or lifting my foot off of the floor.

So all is well as it is for me as it is, but thanks for the ideas.
Frank thumbs

http://franks4x4-solograndetour.blogspot.co.uk/
Combat Stress-http://www.justgiving.com/Roadster100