hanging painting on granite wall

I would like to get some advice on hanging a framed painting (less than 50 lbs)
on a granite wall. Slabs appear to be 1-3/4in. thick and rough surfaced).

The piece now hangs on a drywall wall with triple hanging hooks with D-rings and wire loops and a security (T-screw) screw on the bottom.

My experience is limited to masonry when it comes to harder surfaces.

I imagined drilling a hole pointing down slightly with a diamond tipped bit appropriate for the substrate for each hole (3).
using plastic anchors in the holes and hanging the piece straight on the screws from the wire loops with a washer on the screw for safety.
same idea for the security T-screw on the bottom: hole, plastic anchor T-screw

Any advice would be greatly appreciated.

This is an great question. It sounds to me like you are on the right track but to get input from more folks in a timely manner I would post this on the list serve which goes straight into over a thousand email inboxes out there in the working world. You can post there if you are signed up for the list. You can do it here - http://www.paccin.org/content.php?110-ListServ
If you don't want to sign up I can post it there for you.
Ashley