In the latest development release of ModelConverterX I have included a number of improvements of the drawcall minimizer:

• The performance of the drawcall minimizer has been improved a lot. You should see that it takes a lot less time to calculate the combined texture sheet now.
• There is an additional option to specify that textures with an alpha channel should be excluded. For some objects it works better to keep the textures with an alpha channel separate, for example because they need different material attributes.
• There is an additional option to specify that you want to exclude specific textures from the combined texture sheet. Any texture you select to be excluded will not be placed in the combined texture sheet. You can use this option is a specific texture gives issues or is better kept as well.