not sure whether what i'm saying is gonna make sense

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I will make the mounting of the plexitop as close to the center as possible.
As for the O-ring, i will ask th machinist to make a 1mm(Height) X 1.5mm(Width) trench.. i will order some 1.8mm O-rings.. what do u think about this planning? If no one objects, i will go into Solidworks and edit every single detail, making a trench for the O-ring and some holes for mounting.