Test hit my hairline slightly and I'm not even that susceptible to MPB, no full on baldies in my family, just receded hairlines.
Test with finasteride/dutasteride will be very mild on the hairline.
No experience with dianabol but the above 2 drugs won't work for preventing hairloss with it, you'd have to stop that topically with spiro cream, nizoral, minoxidil or RU.