Looks too thick to me, I'd aim for about 3/8-1/2" on that tank.
That said, I have something of a standard reply for anytime anyone wants to reseal a tank, and that's:
I for YEARS resealed tanks like you're planning on doing - scrapping out the old silicon, cleaning the area well with isopropyl alcohol, and then resealing. Using the painter's tape is a great way to make really good looking seams. Use a grout tool or dip your fingers in water to help smooth out the silicon. I've done this to dozens of tanks, even tanks I don't own. The largest tank I resealed in this way was a 125 gallon that's still holding water 7 years after doing the reseal. I know that I was told like 40 years ago by a pet store manager that you should reseal a tank about every ten years out of an abundance of caution, so that's what I did for many years.
All that said, fast-forward to today where those "in the know" here on R2R have said that it's not a good idea to reseal a tank in this way. The experts say that to properly reseal a tank, the glass panels must be completely separated, cleaned, and the tank basically completely rebuilt, which can be very difficult if you're not in the business of building aquariums.
For me, based on quite a bit of real experience, I think resealing tanks is fine, but please know that many here on R2R would tell you not to do this.
@UncommonSense is very good with these kinds of questions
I hope this helps!
