I measure all the caps I take off & keep a lot of them , parallel or series (series cuts the volts in half, that the cap sees) connections to get that temporary cap. Edit, also, measure every cap I condemn.
You need no calculations either, just measure the beast you created. Parallel volts is the lowest one. Series is more complicated, there is a formula, but the volts the cap sees get very low with each added cap.
But how to mount it & make it safe...
Many new units & compr get replaced from just bad caps.