This is an estrogen crash waiting to happen. I crashed mine on 200mg cyp 50mg proviron, it's in my profile. I thought the same thing get the most out of this small dose of test. Didn't workout to well lol. Crashed estrogen has gotta be one of the worst feelings ever and it takes a long time to get back to normal if you don't up the test dose even after dropping the proviron. Then 600mgs of mast on top of that. His e2 would be zero. That exact provi mast combo controls estro for a few guys here on some heavy heavy stacks.

I wonder how potent 600mgs of mast would be in terms of estrogen suppression on only 200mg of test. I remember rusty saying he was having issues with low e2 using mast as an ai and he was on a higher dose of test. For the op, mast isn't a muscle builder, 200mg of test keeps me in normal range, you'd most likely be shutting yourself down and just replacing what you are making naturally, idk you're natty test levels but 200mgs puts me around 900 which is in normal range, def a little higher then most people's natural test production but not enough to really notice it unless your have low T. I would atleast up the test to 300mgs and probably still drop the mast to 400 or so to prevent it dropping your estrogen to low. if you're set on 600mg mast I'd think you'd need to be running 400mg of test

But why mast when bf is so high? If you're looking to cut fat I'd just use some test e at 400mgs or so. That will have your test levels nice and elevated and will preserve your muscle, and add 50mg proviron. I personally think you'll get a lot more benefits out of proviron at that bf then mast. I love provi, it makes me vascular, harder and drier looking, keeps estro down and its main benefit increasing free testosterone. That would be my suggestion.