plexi is too flimsy, Try the lexan a little more expensive but it doesn't have the give that plexi has. i was thinking the slotted route or at least spacers. and i did let it cure for DAYS actually I think it sat for 2 weeks before i put a rop of water in it but the 2 that let lose didn't have as much silicone as the 2 that are still in place but i haven't touched them for fear of them letting go...I am going to give it another try and this time i am gluing the $#@% out of them peices it will take a whale splashing around in thre after this time