I have found male giants to be mostly docile (the females on the other hand.... ) As for PK and HMPKs, it depends on the individual fish and you'd have to keep an eye on them regularly.
Zui, you've got a great looking tank mate. I'm of the opinion "if it ain't broke, don't try to fix it." You obviously have the right balance in there. I've been screamed at on other forums for having a sorority. I was called a nOOb and was told that my fish would be dead within a month - even though I had stated that some had been together in the tank for 18 months. All I can say is keep doing what you're doing, because whatever it is, it works for you Well done!