@Riot: how does matchmaking compensate for premades?

So the game gives a little MMR 'penalty' to larger premades to compensate for improved communication to a degree where matches are more even, with the goal of getting odds of victory to 50% even if matchmaking has to resort to a solos vs. premade game. Does it give that penalty before finding the remaining members of their team so they are matched with higher-skill random teammates, or only after teammates are found so they are around the same skill level but their enemies are slightly higher (assuming the enemies have a smaller or no premade)?

In previous seasons, premade bot lanes (adc + supp) had a reputation of being much worse than you'd expect, implying it was the first system and you would get two low skill players who were prone to feed in spite of their experience playing together. Even if both teams have the same premade composition there is disparity within the team that can make for a frustrating experiences, although with the second system in the case where premade composition is unbalanced, it can be a very bad experience for solo players who are laning against stronger champions AND aren't even a part of the team with the communication skills to compensate for that.

Both ways seem to create a worse experience for solo queuers, is there a happy medium between the two? what does matchmaking currently do?