I put the waveform of the rendered project into the project itself, and then I had a graph of where exactly those spikes were in the mix. I trimmed them in the mix, rendered the whole thing again, and after like 3 times repeating the process I had a wonderful experience: I could boost the volume to the extend of commercial recordings without distorting the sound.
this is the record I´m talking about (backdoor promotion
isnt it a beautyful waveform?
GAFM ***