The propecia/finasteride/proscar wont help vs Dbol
1)
"While Dianabol does convert to a more potent steroid via interaction with the 5-alpha reductase anzyme (the same enzyme responsible for converting testosterone to dihydrotestosterone), it has extremely little affinity to do so in the human body's. The androgenic metabolite 5alpha dihydromethandrostenolone is therefore produced only in trace amounts at best. The benefit received from Proscar®/Propecia® would therefore be insignificant, the drug serving no real purpose."
from Llewellyn, William, Anabolics 2004, 2003-4, Molecular Nutrition, pp. 93-6
2)
Methandrostenolone has an added cis-1 to cis-2 double bond that reduces both estrogenic and androgenic properties. However, it does undergo aromatization to the rather potent estrogen 17-alpha methyl estradiol, but curiously does not show the in vivo propensity for reduction by 5AR to alpha dihydromethandrostenolone to any large degree.
from Steele RE, Didato F, Steinetz BG. Relative importance of 5alpha reduction for the androgenic and lh - leutenizing hormone - - leutenizing hormone - -inhibiting activities of delta-4-3-ketosteroids. Steroids. Mar 1977;29(3):331-48. [Medline].
3) I know Bill Roberts is also of the same opinion, but cant dig up the link