I have a couple of dozen O. scyllarus in glass 20 L tank and none of the tanks have been broken. On the other hand, the tanks are all on fiberglass aquarium racks in a room with epoxy floors and floor drains and the electrical drops down from the ceiling. Should a tank leak or break, all I will possibly lose is the stomatopod. That is very different from having a tank in your living room. The risk of breakage is very small, but if the consequences are large, it is probably prudent to use tanks with at least 8 mm glass or line the bottom with thin Plexiglass or other plastic.
I've written on this subject many times, so I won't re-hash the obvious. I have tried to recall all of the tanks that I have had broken by O. scyllarus. I came up with 8 - not including the time that I trained an animal to break tanks for the BBC. The most memorable was in 1974 when a true 7 inch male named George took out the face plate of an "Instant Ocean" 35 gallon tank while the editor of Scientific American was watching. That animal double dactyledly helped launch my career because the editor was so impressed he asked me to write an article for the journal. I wish I had had George's raptorial appendages bronzed.
Given that I have been keeping O. scyllarus in my lab since 1972 and have had probably over a thousand including very large animals that are no longer available, only 8 disasters is a pretty good safety record. (But even then, the really big guys over 6 inches went into Plexiglass protected systems.)
The bottom line is that it is up to you how much risk you want to assume. For me, if I were to keep a 6 inch O. scyllarus in an aquarium in my living room over my wife's prized hardwood floor, it would be in a very well armored tank. The cost of failure would be way too high.
Roy