Two points which might help:
1. Calculated metrics (as opposed to model metrics) will not work in tables locked to two model objects, because a calculated metric has no way of knowing how to allocate itself from one object to the other.
One workaround though is to insert a new report table column which uses the same formula as the calculated metric's formula.
For example: the calculated metric called Cost YTD won't work in a table locked to both Cost Source and IT Resource Towers. But since Cost YTD = YearToDate(Cost), we can just insert a new column into the table (already locked to two objects) such as YTD Cost = YearToDate(Cost). Since the report table knows how to calculate Cost, the new column will work.
2. Individual allocation lines from a model can be used directly in report table column formulas. Each object's inbound allocations are individually listed and available from the Calculations perspective in the ad hoc query configuration dialog.
For instance, here are the inbound allocations for the IT Resource Towers object in my Cost model:

...these can be combined or mathematically manipulated just like any other metric such as Cost.