Not sure if I've mentioned this before but it's a misconception that SG necks are heavy, thus the neck dive syndrome. I think SG necks are just as heavy as LP necks, if not lighter, but their body is lighter and the fulcrum is further towards the body, thus the natural tendency for the neck to succumb to gravity.
My simple solution? Buy a strap that sticks to your body/clothes. Don't buy those w/ smooth surface (eg, leatherette). Better pa yung magaspang na side ng leather. I also naturally push down the body w/ my picking forearm, thus helping keep the neck up.