The deck has the right idea, but the wrong way of doing it. You should build your decks as 75 cards, then moving the weakest 15 cards to your sideboard. You just have to do that beforehand, not in game 2 lol. This has long been a technique for sideboards, which is the hardest part of deck construction. Having the right mana curve, correct number of threats, etc. is where people run into problems when boarding.