From my understanding, Uni seals are designed to be used with buckets < rounded > and bulkheads are better suited for flat totes. Having said that, both can be used with either bin. Your pipe should be very hard to insert in the Uni seal as this is the main compression against your cut hole. In fact usually some lubricant or dish soap is needed and another tip is to sand the outer edge of your pipe to help get it started. In your situation it is probably easier to find pipe to fit the Uni seal but if you do decide to switch seals, go with bulkheads with those totes. Good luck.