as you know one reson to use short cycles like 2on 4off is to avoid shutdown but heres something that talks strongly against that:

The Journal of Pharmacology And Experimental Therapeutics, Vol 281, No. 1; 93-102, 1997.

HPTA Suppression Is Imminent

Anyone who’s used anabolic steroids for any length of time will easily observe that when they discontinue using, they invariably "crash." That is to say, their body is producing next to zero endogenous androgens. This can lead to significant loss of muscle gain, loss of strength gains, lethargy, depression and a whole host of other disorders. Of course, drugs like HCG, HMG, clomiphene and similar gonadotrophics can help to ameliorate such symptoms, but these aren’t 100% cure-alls. The success or failure of such secondary drug use varies considerably between individuals.

This study utilized ten healthy male volunteers who were randomized to receive either the phenylpropionate or decanoate ester of nandrolone via intramuscular, oily depo injection. A single injection of only 100 mg of nandrolone phenylpropionate caused almost complete suppression of endogenous Testosterone by day three and lasted until around day eight.

Endogenous levels of Testosterone didn’t return to baseline levels for almost fifteen days, while the same type of injection with nandrolone decanoate caused almost complete inhibition of endogenous by day four. Endogenous levels of Testosterone didn’t return to baseline levels for greater than twenty days! All this from a single, 100-mg injection of nandrolone!

This tells me that no matter what you do, whether it’s a short lasting ester or a long lasting ester, you’ll end up totally shutting down your body’s ability to make androgens for at least two to three weeks. Since nobody (well, at least nobody male) uses only 100 mg of nandrolone per week, it’s reasonable to conclude that the suppression caused by 500mg of an esterified anabolic per week (an average dose) would be much greater than two to three weeks. This study didn’t deal with fast acting orals like stanozolol and oxandrolone, but there’s no reason to think that these won’t cause HPTA insult as well.

It means that HPTA insult is inevitable and should be planned for accordingly in your cycle. That is to say, you should plan on crashing for a few weeks post-cycle no matter what. Because of this, you’re going to want to extend and "beef up" your cycle so that you overshoot your final goal.

This tells me that no matter what you do, whether it’s a short lasting ester or a long lasting ester, you’ll end up totally shutting down your body’s ability to make androgens for at least two to three weeks. Since nobody (well, at least nobody male) uses only 100 mg of nandrolone per week, it’s reasonable to conclude that the suppression caused by 500mg of an esterified anabolic per week (an average dose) would be much greater than two to three weeks. This study didn’t deal with fast acting orals like stanozolol and oxandrolone, but there’s no reason to think that these won’t cause HPTA insult as well.