you need estrogen and its conversion on cycle to reap your best gains ....the conversion processs increases igf levels and nitrogen retention.....a good reson test C or E are top choices for your primary hormone during a bulk.....
that said you always want keep your e2 at a optimal level.....regardless of the "feel" method or " my nips arent sore" method which are pretty much horrific indicators....keeping your e2 in range simply adds up to more free testosterone....and thats much more important then total testosterone....i do best with mine around 25ish range ....but anything in mid range is fine..