Most players will get gauze around the 5 minute mark.  I suggest you scout their base say around the 4 minute mark to see if they have 3rd reactor going.  And if you do happen to run into a hog while scouting watch the fire.  Is it just guns or does he have the launcher too.  If he has a launcher already sure bet he'll get the gauze too.

You can expect good player to recycle their reactors once they start the gauze upgrade.  Key word is start.   I do as soon as i hit upgrade, i'm blowing up reactors and replacing them with supplies while I'm still upgrading the gauze.  The supplies I get back in doing so is huge.

Scout Scout Scout!! Not just once either! You have to keep checking.  If you scout me, I'll change up what I'm building just because I saw you see me.  So go back and check a few seconds after you split the base.

Peace!!!