No, inhibition of 5-AR wouldn’t give you
significantly higher levels of nandrolone
as a result of blocking conversion to DHN,
because it’s only a very minor fraction
of nandrolone that undergoes that conversion.
I doubt you could even measure the difference
in blood levels.
And if you did decide to inhibit 5-AR to
obtain this dubious and small-at-best benefit,
you’d have a much more potent androgen in
your scalp (nandrolone) than you would have
if you hadn’t tried this idea. So using
numeric examples as you did, which is better,
being able to take only 390 mg of Deca instead
of 400 and getting the same anabolic effect,
but getting much more effect on the scalp;
or spending a few extra pennies on Deca and
using the full 400 mg and enjoying the benefits
of 5-AR largely deactivating it in the scalp
Nandrolone does aromatize but not very readily,
and will uses of up to 400 mg/week estrogen
levels DROP relative to baseline rather than
increase. At high doses maybe estrogen can
rise above normal but that is just a guess.
The only thing I have seen is drops in estrogen.