I think one of the issue contributing to the poor FPS in the Carenado ATR 42/72 is the size of the .mdl that are + 100mb in some cases models ot +200mb just the internal model and +100mb the external model also with layers and layers of textures bump and spec, is unnessesary to have such big models, even the PMDG 747 model size is around 24mb.
This large is ridicoulus for an ATR