Pisshead not sure what you are asking about combining 20% with 50%.
On a stripping run everything goes in the same jar mate no matter what the abv is. These are called low wines and once you have enough low wines to do a full run all the low wines are combined, watered down to 40% or under if needed then run as a spirit run.
From the spirit run you will then be tasting and making cuts, and product from a spirit run that does not make the grade is kept aside as feints u til you have enough to do a spirit run of feints. Again you make the cuts and any left overs are thrown out, used as fire lighter, de-icer for the windscreen , cleaner , anything except drinking
I hope that makes sense and answers your querrie