HDR and AA are killers but keep in mind you can make adjustments in the UI along with the default rendering settings to increase performance. We included these options so that SkyMAXX can be tailored to a large range of systems... I would start by setting "cloud detail" to its lowest setting and "cloud draw distance" the same.... Keep the cloud sizes smaller also, once you have this make incremental increases until you are happy with the output.... Crepuscular Rays are going to be expensive, no way to get around it. If your system has a terrible time with them just shut them off, but by tweaking some settings in the UI and default rendering you can get them to work well..... Two other performance tweaks we included are the cirrus texture resolution and 3 different overcast layers..... Selecting low or mid cirrus layers help slightly with a smaller texture load... Out of the three overcast layers "Med" is my favorite, a flat overcast layer is there for performance also in the "low" setting. "High" uses ray-casting and is recommended for power users.....