I recently purchased a used Cad Lights 42 gallon tank, and wanted to purchase all new plumbing for the tank, but noticed the drilled holes are 42 mm and 22mm. I cannot for the life of me find any bulkheads for a 22mm hole, so I am looking into possibly redrilling the hole to a 35mm hole. I am planning on putting a 3/4" SCH 80 bulkhead in the 42mm hole, and a 1/2" SCH 80 bulkhead in the newly drilled 35mm hole. Is it a bad a idea to drill over an existing hole?