for a 100 gallon tank, i would just buy a manufactured rimless ADA tank. Its gonna be costly, but it comes with a 5 year guarantee. It might be cheaper to make one yourself, but if it breaks, you are screwed with no one to blame but yourself, and no way to get reimbursed.
im sure of the many who have tried to make thier own rimless tanks, few tanks have really lived up to the builders expectations. And my guess is, the larger the tank built, the less likely it will work due to weight, and design shortcomings.