It is more important to open the rear face fuselage hole and tailcone hole around the tailpipe. The tail cone gets quite warm without the air gap.
The new Evo built in under 5 days was test run by the builder without opening that up and the tailcone got hot. Added some clearance and we ran it yesterday and it was pretty cool.
You can see he went with the NACA ducts having built previous fully ducted UF’s