I just wanted to say that using a garbage disposal sink lip thing (or whatever it is called) is a great idea. I tried using pvc like I saw other people doing, but it always deforms to the point where it can fall in if you don't catch it in time. Using metal is a must.
As far as the bag is concerned, if it is full of hops it will pick up enough weight in water to sink. I couldn't tell if you have a collar holding it on, but if you do, I would recommend flipping it over in the other direction shown in the picture. The nylon between the collar and garbage disposal lip can get very wet and slippery...then with all of the weight from the hops in the bag...when you go to lift the spider out the whole bag of hops can potentially pull the collar off. It's just something to think about...what I do is similar to your picture, but flip it over and stuff the bag through the center for added friction.