As I suggested in that thread 4 days ago “You might like to try silencing some of the horns for that particular passage. To do so, select the notes for perhaps 6 of the 12 horns then open the lower zone (Properties) and, in the Common section, enable Suppress playback.”.
If I have understood your differentiation between dynamic and volume, this will keep the dynamic the same but reduce the volume because there will be fewer horns sounding. Have you tried it? It might work.