Visiting a Sumo Training practice

we will be in Japan in April 2014 and would like to visit a sumo training practice .. since April is NOT a tournament month, I understand this is possible. Our dates/cities are flexible (though we would prefer Tokyo).

I've checked several websites/tours and would appreciate any recommendations for one that is the most authentic and non-touristy (small group, view from inside the stable, etc.) .. also will need an english speaking interpreter.

Thank you.

I found the following good and easy to pay with Paypal:
http://ijcee.com/english/fascinate/walk/sumo.html

The tour guide is essentially just the means to get you access to the stable. During the morning practice you are not supposed to talk.

I've only been to Sadogatake years ago when it was an organized trip by the university I was attending. It's very authentic, small, and you're not supposed to talk, move, or do anything else than watch for 1-2 hours. Afterwards you can't even exchange a word with anyone and have to leave.

We watched for nearly 3 hours (it felt like 45 minutes, though) until the practice was over. Afterwards, we met some of the wrestlers outside in front of the stable, exchanged some words and took some pictures together. One of the best experiences ever.

It was the Kasuganobeya.