Re: Some Details.

Earl,
That mixed valve gear nightmare has happened - there is always a prototype for everything! Some genius in the UK built a locomotive (or class of locomotives) with, I think, outside Walschaerts and inside Stephenson gear. I can't recall the exact details but I'm sure that one type increases the lead as it's linked up and the other reduces it.... I can't remember who or where this disaster happened but it only goes to show that some personnel were not up to the job.
Re the D&RGW M-69's - I had to look closely at the photographs to see what you were talking about. I think that the German class 44 2-10-0 had the third set of valve gear driven off another axle from the normal set but I can't find a picture of one at present ( and apparently not all were the same).
G