While I agree 100% what the purpose of this 40 hrs. I don't see in the
regs where is requires the DAR to impose a a limitation to a single
airport.
I see my friend's point that it would be nice to be able to land at an
additional airport within his flight test area.
The flight test period is also the same weather you are testing a new
radical design or your 3rd RV with a lycosaurus.
Considered the difference in time required between the same airplane
with a certified engine or with a certified engine that the DAR will
not consider a certified engine? What additional flight testing are
you planning for those 15 hrs?
Just saying, if the FARs don't prohibit it, it might be nice to be
able to land at an airport in your practice area and get a burger
between flight tests.