[froggsong]

In my experience, it is NOT necessary to spread silicone under GS sprayed directly on glass... Other than the fact that it looks better from the outside. The landings I did straight on the glass have held up much better than the ones I did off the glass and siliconed on later.

It is VERY easy to make GS landings like you want, all you have to do is make sure that the tank is laying on the side you want to do it on, and then build in small layers until it is as high as you want, then carve and cover, and then turn the tank so that it is right side up, and the landing will stick out however you wanted it to. Just make sure if you want landings on different sides that you let each one cure before turning it to the next side to do the next landing. I did them in my frog tank like that. It was my first time using GS, and they turned out fine. I had to remove the landings from the glass when I broke the glass part of the tank, but I was still able to put them back in. So, if something happens and you have to remove them for any reason, don't just discard them, because you can use them again. Also, if you want a landing to extend out really far, it is advisable to put something strong into the GS to keep it from sagging, like a length of thin PVC or something. Really really long landings may need a support from underneath as well, so they do not sag or disconnect from the wall due to the weight.