Ah, this is brilliant! I get you now.
If I understand you correctly - your goal is to measure how effective your process of picking a portfolio is - not to measure the actual performance of the coins. If you can repeatedly do a good job of researching and deciding, the actual performance is likely to work out in the long run.
Is that right?
Yep. Exactly that!
Focus on the process and not the outcome - then once you've developed a skillset the performance will come.
:D