Adding 4 links to my MTB chain

Wheels of Happiness

This post installed a 42t cog to the MTB.  (from 36th)   So thats 6 additional teeth and the RD looks a little bit stretched and ready to break.  So I decided to add 4 links from extra chain length I hid when I changed my chains.    I thought of having the bike shop install this, not quite trusting my chain installation skills.  But later during the day, I decided I could do this.   I hope the chain would not break come hill climb time.