N17E potency?

Bill has mentioned that N17-E will approximate 400 mg of nandrolone in potency while T17-E might equate to 600 mgs of T. Is there a reason for limiting the strength of N17 other than a potential protestegenic effect of nandrolone over approx. 400 mgs? Also, I know this might be a ways off but any idea as to when T17 might be available? I realize that it is very early to ask that but even a rough guesstimate would be appreciated.