How to change the 'Ground' from Terrain 3D to custom elevation surface in My Scene Arc GIS Online?

[JoshuaWebborn]

Hi, 

I am trying to display two different elevation models in Arc Scene online in 3D. However, my elevation layers are being applied to the default Terrain 3D elevation surface which is not true to my elevation layers which have a custom elevation surface

Is there any way of changing this in My Scene Arc GIS Online?

Thanks

[JimChapman]

Would love an answer to this question, too!