Connect 2 mono nodes as L/R input for a stereo node

Hello, I'm fairly new to AVAudioEngine and I'm trying to connect 2 mono nodes as left/right input to a stereo node. I was successful in splitting the input audio to 2 mono nodes using AVAudioConnectionPoint and channelMap. But I can't figure out how to connect them back to a stereo node.

I'll post the code I have so far. The use case for this is that I'm trying to process the left/right channels with separate audio units.

Any ideas?

                let monoFormat = AVAudioFormat(standardFormatWithSampleRate: nativeFormat.sampleRate, channels: 1)!
                
                let leftInputMixer = AVAudioMixerNode()
                let rightInputMixer = AVAudioMixerNode()
                let leftOutputMixer = AVAudioMixerNode()
                let rightOutputMixer = AVAudioMixerNode()
                let channelMixer = AVAudioMixerNode()
                
                [leftInputMixer, rightInputMixer, leftOutputMixer, 
                 rightOutputMixer, channelMixer].forEach { engine.attach($0) }
                
                let leftConnectionR = AVAudioConnectionPoint(node: leftInputMixer, bus: 0)
                let rightConnectionR = AVAudioConnectionPoint(node: rightInputMixer, bus: 0)
                
                plugin.leftInputMixer = leftInputMixer
                plugin.rightInputMixer = rightInputMixer
                plugin.leftOutputMixer = leftOutputMixer
                plugin.rightOutputMixer = rightOutputMixer
                plugin.channelMixer = channelMixer

                leftInputMixer.auAudioUnit.channelMap = [0]
                rightInputMixer.auAudioUnit.channelMap = [1]
                engine.connect(previousNode, to: [leftConnectionR, rightConnectionR], fromBus: 0, format: monoFormat)
                
                // Process right channel, pass through left channel
                engine.connect(rightInputMixer, to: plugin.audioUnit, format: monoFormat)
                engine.connect(plugin.audioUnit, to: rightOutputMixer, format: monoFormat)
                engine.connect(leftInputMixer, to: leftOutputMixer, format: monoFormat)
                
                // Mix back to stereo?
                engine.connect(leftOutputMixer, to: channelMixer, format: stereoFormat)
                engine.connect(rightOutputMixer, to: channelMixer, format: stereoFormat)