With a good soft mount you wont see the cracking of the rigid headers. The new Hatori 822/823 series headers with an 821 short pipe is virtually bullet proof if you use a good soft mount. The engine will move, but with the way the pipe mounts it will flex as well. The biggest thing with this setup is leaving enough space where the header fits into the pipe to allow for expansion for heat. If you do, you wont see any issues. I had over 2200 flights on my last plane with no headers broken with this setup.

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