Making Wholemeal/Whole Wheat Sourdough Bread?

So recently I've gotten into making Rēwena Parāoa (Māori fermented bread), basically its sourdough bread using potato as a sugar source for the bug. Tasty stuff.

I've been using a ratio of 1 part bug, 2 parts water, 3 parts flour.

It works fine enough for white (all-purpose) flour but for wholemeal (whole wheat) flour I've noticed I don't get much of a rise.

How do you go about adjusting the ratios?

How much bug should you use for whole wheat, or even rye flour?

Cheers.