The problem is, the greater the share of the constituency seats, the greater the probability that you have overhang seats. This depends on the structure of the party system. If you have a more or less fragmented party system so the biggest party has about 30%, it is possible to win almost all of the constituency seats. If you have more than 30% of the constituency seats, this party would have overhang seats. It depends on what you expect the share of votes that the biggest party can achieve.
In Germany, they usually have a fifty-fifty division. This was not a problem until the reunification in 1990, because the biggest parties always had about 45% or 50% of the second votes. Even if they got all constituency seats, there were no overhang seats. However, with an all-new party system after the reunification—because we had a strong leftist party in the eastern German Länder—you could also win with 35% of the votes, almost all direct seats, constituency seats, so you would have 50% of all seats with only 35% of the votes. The number of overhang seats has increased dramatically since 1990.