Silicone bulkheads - gasket or not

[Rikko]

I had a hell of a time getting the bulkheads drip-free when I plumbed my 120, but I finally got it to work with no silicone.
My first try around, I used the gasket on the inside and silicone on the outside.. Drip drip dip.
Second time, silicone on both sides.. Drips!

The third time, I forewent the silicone and just used one gasket and tightened the hell out of it.. Drip!

Finally, I hand-tightened in, but only about as strong as I could do with my left hand (being right handed).. Not a single drip in six months..

Though I see a drip forming in my drain line plumbing... I think the next time I do this, I'll splurge and use PVC primer before cementing!