EDIT!!  After a very negative one star review regarding tolerance, I tested printing the uprights standing on the build plate and placing a brim around them.  Works flawlessly, so if you are having trouble with the uprights splitting when printing flat, stand them upright on the build plate.

Print as many uprights and holders as you need. It should all fit together well!

Edit: make sure to print the holder on its side so it forms a sort of letter 'W' shape on the bed. You may need some spots of super glue to hold the parts in place once assembled.

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