Dave,
"All of the FSX models demonstrate an artifact in DX10 but not DX9. A black line appears on both nacelles top and bottom, back to the U/C doors. This is most likely caused by texture stretching affecting bump mapping. Therefore, DX10 needs to be turned off when flying the Beaufort in FSX. The aircraft is fine in P3Dv4.5."
I'm running FSX Steam Edition along with Steve's DX10 Scenery Fixer v5.3 and all seems well.
Tommy