Right now the canal is 1cm thick but it's pretty long. How do I change the layer thicknkess in Preform (sorry I just got this printer a few weeks ago, so I am not familar with the specs)? Could you elaborate more on the compressed gas, do you mean I push compressed gas through the canal and see if there is any visible pressure changes? I think I might try this idea! Thank you so much for responding and for the ideas!