Alan, I mixed 500ml of the concentrate and was going to try it out on some Delta 100. But with the 1+9 dilution I'm not really sure what development time to try. I guess I could try 6min as you have done, but at this dilution the working characteristics will be significantly altered. At the working dilution the formula now bears more of a resemblance to compensating-type developers, which may help with an effective speed increase. I'm still expecting relatively high fog though, given virtually any Phenidone developer with a pH this high uses a restrainer.
I will see what I can come up with in the way of sensitometry, but I wonder if this development time will even be in the ballpark.