Maybe the problem is that you have the 20-man team. There is no coherence in the code. The design is wrong, coupling is too high, and the module cohesion is too low. The large team makes certain that is the case no matter how "tight" (aka heavy) your quality control process.

I have found from working in large teams, there is a core four who get things done. The rest are simply dead weight dedicated to shuffling paper and attending meetings. At best, they do nothing. At worst they create more work than they do.

Use the right four and dump the other sixteen. You will get at least ten times more productivity and ten times higher quality without even breaking a sweat. If you don't have the right four, you are hosed from the start.