How to use custom masks with flood tool?

Hi All!

I've been following this tutorial to help with Quadspinner Gaea: https://infotoast.org/site/index.php/2023/03/06/how-to-use-quadspinner-gaea-for-minecraft/

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I'm wondering, when I use the rivers map provided by quadspinner with the water block, it seems to create broken rivers, often non-flowing water, blocky, which when updated in Minecraft can spill in undesirable places.

Is there any way to use the flood tool/substitutes with the masks created by Gaea to create rivers that flow across the land more naturally?