Paul, I just saw this topic so if you’re still looking for help with this, I have some details about how I do my bathymetric maps in this old thread: https://discuss.inventables.com/t/cribbage-around-the-lake/16214
I’ve done many Lake Superior ones and a few other miscellaneous lakes. The one-off lakes aren’t really worth doing because it’s a bit time consuming to get ready for actual carving.