The Stainz is owned by Geof. His website is here
http://www.trainweb.org/btr/Latest News.html
- you can find his email address on his Links page. I'm sure he'd be happy to tell you how it did the conversion and how long it runs. He has a good description here:
http://www.trainweb.org/btr/Stainz.pdf
He is also on GSC as geofc if you'd rather send a PM
I'd suggest the trick to doing small engines is to find the minimum number of AA NiMH for the speed you want and then figure where to stuff them in. Cells around 2000 mAh will give you many hours running I'm sure - that's what I generally use for even larger locos.