Regarding the safety of rimless - Skriz is certainly right... if built correctly, they are super-safe... in fact, the builder of my tank (A.G.E.) claims to have NEVER had a rimless fail.
here is a pic of the bottom of my rimless tank / overflow i had custom built (production pic)...30" wide tank. They use a CNC router to machine in pvc board where the glass will be laid-in (for the tank walls) and the overflow... another nice touch, they actually cnc'd the "Hex" shape for the Hayward Hex sch 80 bulkheads to fit so they are self-tightening... pretty neat.
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here is a pic of the bottom of my rimless tank / overflow i had custom built (production pic)...30" wide tank. They use a CNC router to machine in pvc board where the glass will be laid-in (for the tank walls) and the overflow... another nice touch, they actually cnc'd the "Hex" shape for the Hayward Hex sch 80 bulkheads to fit so they are self-tightening... pretty neat.