most hardwoods that are very dense, and also have a higher janka rating will tend to shrink, only way to combat this is to make sure you have environmental controls in your house to ensure you have a consistant humidity levels all year long.

If you like cumaru you can still have it, if you have a decent hvac system installed you will hardly notice the shrinkage.

You are going to hear from people to just go engineered, which is not a bad recommendation but if solid is what you want, you are going to experience some shrinkage.

Do you have an installer lined up yet to do this project? if you do or not, try to see if he's done a job similar to this before and see if you can take a look.

Thanks for your comment. After a bit more thinking we ordered some samples of brazillian cherry. Our installer has not done cumaru before. In terms of shrinking and look of the floor as it wears, does the kind of edges it has make a difference?