surfur- looking realy good so far. I dont know if agree with some of your tears on the leather. You seem to have the under leather being stressed and torn but the straps that are above these area far less stress. also maybe some dirt or drip marks under the bolts
Yes it has to do an extra call but its not that horrid a deal. Any transparent item will need to be sorted and drawn over the other things in the scene, and any material change will need another draw call, etc etc. There are technical tradeoffs between how well your engine batches geometry, how your shaders are set up, and…