I only now realised that some people actually use the infamous “DX10 Preview” mode in FSX, which may explain some of the more mysterious bug reports I have received over the years. So I will try to sum up how this mode affects FSX in general, and Draken in particular, and then you can decide for yourself if you want to use it or not.
DX10 was never fully implemented in FSX, but a “technology preview” mode was thrown in to show what could be expected in future versions of MSFS. It has generally been recommended to keep this box unticked, as the results were erratic and could even crash the program. The user would typically see flickering texture maps, disappearing airport and aircraft lighting, etc.
Today there are third-party patches available that makes it possible to fly with DX10 mode enabled without too much trouble – although there are still some problems, mainly concerning lights and effects which function unpredictably or not at all.
I have been testing Draken in DX10 today and it works perfectly well except for the lights and smoke fx. These fx have now been updated to be DX10-compatible, and I will upload an update package ASAP. Some detail textures are also not working well with DX10, they will be replaced in the final release.
I do not support using Draken in DX10 Preview mode, but I will at least try my best to make it work as good as in DX9.