sink falling cont.....can I put supports myself????

Guy's,
If the installers won't come back and (http://maplered.com) put more supports for my sink, can I do it myself? I have 1&1/2" space in front of the sink. I could put a 1x1" plywood across the front. In the back I have 4". I could use small blocks of Granite (http://tanbrown.org) to silicone in a few places. What do you think? You guy's could walk me through it. What kind of silicone would I use? Fast drying I hope Where can I buy the silicone? I'm good at doing my own repairs, so this shouldn't be a problem. This way the sink won't sag.
I know you said the Granite (http://tanbrown.org) won't crack but I'm still nervous.
Donna