Couple more test prints

Same result with one. A different distortion the other.

The print orientation for the first and second test was the same.


There more surface area in the cross section to break loose from the FEP. The pull/suction is causing the distortion on outside surface. The reason for this angle was to minimize the number of supports in visible areas.
The second test print was rotated. There will support marks on visible areas.

There is a much smaller cross section through the bulkhead. Making it easier for the part to release from the FEP.
As for the distortion on this test print. It may (likely) have been caused by the user. I unwittingly changed the supports from medium to light.
There are multiple solutions for the distortions.
I can use heavy supports for the vertical orientation. Increase the number of supports for the bulkhead. I'll cut the engine shorter because the print is 5-1/2 hours.
Reprint the horizontal version with medium supports. A 3 hour print.
I will remove the lower engine cowling and print that separately. That might make sense for the vertical version too.
I may reduce the size of the return on the underside as well.
I'm early in the process of this build and I don't want bog down the rest of the parts.
At this point, I will just peculate on this.
Maybe thinning the web or making it with lightening holes or triangulation would stop the pull.
Thinning might help but I don't want to add holes that I would have to fill.