Using Variance Explanations and UD8 (Dynamic calc periods) together

Hello: We'd like to incorporate variance explanations into our cube views.  If the cube view shows one periodic comparison (e.g. Jun YTD CY vs June YTD PY), we have a corresponding dynamic calc that calculates the variance and we can use the (out of the box) variance explanation from the View dimension in order to have comment/explanation functionality.

However, if we have multiple comparison period in the same column template/cube view, we are unable to.  If we take the same approach as one periodic comparison, the same comment would appear in both comparison columns since there's nothing to distinguish which periodic comparisons are being explained against.  

We tried using a placeholder UD8 elements (no formulas) in addition to the variance explanation from View dimension but OneStream says it's an invalid cell. 

Advice?