I used silcone on my first project when I first started 5 or 6 years ago. I built the overflow/weir on melevsreef. I worked took a while to set up and I am actually still using it. Silcone works but the Weld-on is a lot easier and quicker. Learn to use the 3 or 4, once you do you find the thicker stuff very cumbersome. Practice on a couple of pieces before doing you actual glue up.
Kent