To all of those who have worked the front heatsink and paste. How tight did you go when re-attaching? I normally wouldn't be paranoid about things like this but it seems like they weren't that tight from the factory at all. Certainly don't want to crush any SMCs.
Tighten until resistance?
There is WAY too much BAD information in this thread...from overclocking to advice...WOW
STEP 1: VERY IMPORTANT!!!
Update the firmware IMMEDIATELY, and do not tick the box to save settings....you will have to wait a few minutes...lets say 3 minutes TO BE SAFE..DO NOT POWER CYCLE THE UNIT WHEN UPGRADING...then re-enter all your pool info...if this is too hard to do, then shut your machine off and call it a day...
I have done the front and back heatsinks....the front is not really what needs the proper surface contact as much as the back...hate to break the news but after reading through this thread I cant stop cringing...and don't know where to start...so here we go... since you only are concerned about the tiny little heatsinks which clearly are not as important as the MASSIVE ones in the middle of the unit
DO NOT USE ARCTIC SILVER 5 IT IS CAPACITIVE..OR ANYTHING WITH SILVER IN IT.... STOP THIS NOW and if you have done this....get cleaning using a proper electronics alcohol FFS 
Not Electrically Conductive:
Arctic Silver 5 was formulated to conduct heat, not electricity.
(While much safer than electrically conductive silver and copper greases, Arctic Silver 5 should be kept away from electrical traces, pins, and leads. While it is not electrically conductive, the compound is very slightly capacitive and could potentially cause problems if it bridges two close-proximity electrical paths.)some good grease to use is GC Extreme but a little thick for large application...GC Supreme works much better for that....
as for attachment of the semi-useless heatsink...do all 4 starting with the outside ones first then the inner 2, then tighten them 2 off kind of like when you change a car tire..if you don't know what I mean then I suggest learning how to change a tire properly for starters..bolts make all the difference but I digress
As for clocking/stable running units...I am working on the how and why...so far I have seen every unit behave differently and hate to say it but the grease did not help the hashrate drop AT ALL
BITMAIN really needs to fix the firmware on these units...at least make a universal interface...this one is a hack of S1/S2 but missing all the basics like not having the page timeout, the option to have password saved in browser for starters
More important, there is a bug in firmware which shows inaccurate stats, for example when power cycle the unit, it shows uptime of 8 hours and the unit showing 1 minute, resulting in WRONG average hashrate for many hours
I've been poking about the front-side HS for a minute simply because BMT emailed me instructing me to do so. I believe they've emailed a few other users giving instructions to do the same. Regardless of other's experiences, my front-side HS went from cold to the touch (ineffective) to very warm after the cleaning.
I HIGHLY doubt it has anything to do with the paste and most to do with the fact that the heatsinks were not tightened down at all in the first place. You can talk bout spring tensioners all you want, but with how roughly those HS blocks were made, 3/4 of my springs were caught on aluminum burrs.
