CakeBaker - There is not really a science as to how many dowels to use per tier. If you are worried about the structure you can always add a few more -
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AMACOAM Cake Board Thin Cake Boards 6 Inch 8 Inch 10 Inch 12 Inch Round Silver Cake Board for Tiered Stacked Cakes Cake Drum Coated Cardboard 2mm Thick for Decorating Wedding Birthday
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NACAIKJ 4Pcs Cake Boards Round Cake Board for Tiered Cakes Thin Cake Boards 6inch 8inch 10inch 12 inch Silver Cardboard for Tier Cake : Amazon.co.uk: Home & Kitchen
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AMACOAM Cake Board Thin Cake Boards 6 Inch 8 Inch 10 Inch 12 Inch Round Silver Cake Board for Tiered Stacked Cakes Cake Drum Coated Cardboard 2mm Thick for Decorating Wedding Birthday
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AMACOAM Cake Board Thin Cake Boards 6 Inch 8 Inch 10 Inch 12 Inch Round Silver Cake Board for Tiered Stacked Cakes Cake Drum Coated Cardboard 2mm Thick for Decorating Wedding Birthday
![AMACOAM Cake Board Thin Cake Boards 6 Inch 8 Inch 10 Inch 12 Inch Round Silver Cake Board for Tiered Stacked Cakes Cake Drum Coated Cardboard 2mm Thick for Decorating Wedding Birthday AMACOAM Cake Board Thin Cake Boards 6 Inch 8 Inch 10 Inch 12 Inch Round Silver Cake Board for Tiered Stacked Cakes Cake Drum Coated Cardboard 2mm Thick for Decorating Wedding Birthday](https://m.media-amazon.com/images/I/514WLMHUpgL._AC_UF350,350_QL80_.jpg)
AMACOAM Cake Board Thin Cake Boards 6 Inch 8 Inch 10 Inch 12 Inch Round Silver Cake Board for Tiered Stacked Cakes Cake Drum Coated Cardboard 2mm Thick for Decorating Wedding Birthday
![NACAIKJ 4Pcs Cake Boards Round Cake Board for Tiered Cakes Thin Cake Boards 6inch 8inch 10inch 12 inch Silver Cardboard for Tier Cake : Amazon.co.uk: Home & Kitchen NACAIKJ 4Pcs Cake Boards Round Cake Board for Tiered Cakes Thin Cake Boards 6inch 8inch 10inch 12 inch Silver Cardboard for Tier Cake : Amazon.co.uk: Home & Kitchen](https://m.media-amazon.com/images/I/61ye+-1b4NL._AC_UF894,1000_QL80_.jpg)