Will the MT1 model work with an existing Bimini on a 2004 Rinker 212 Captiva? Are there additional instructions/cautions when installing? Should the existing Bimini go over or under the tower?

We typically recommended our towers would not work with factory biminis. The top of the top narrows and typically cuts off the space the factory bimini would need to use as well. That being said we have seen it work as well. There is no way to tell for sure until you have the tower and factory bimini together.