Lining up runway 05R at Dusseldorf, Germany [EDDL]
Overflying Zurich area, Switzerland
Crossing The Alps southbound
Hand flying localizer approach into Calvi, France [LFKC] with Flight Director and Autothrottle off
If your computer cannot handle the IXEG, it cannot handle X-Plane. The 737 Classic is the best optimised payware aircraft I have ever seen. Having just bought the FSLabs A320 for FSX and spent an entire weekend trying to get it to run smoothly on a pretty high end rig, I can say IXEG have performed miracles with this plane. It ran smooth straight out of the box.
In my computer (Qcore i5 4GB and AMD R9 380 2GB), with SkyMaxx Pro 3.3 I los 25-30% of FPS. I do not have this problem with others planes; for example, MD88 Rotate.