I have been experimenting with a modle with suitable designed slatted vertical fin and engine power as low as possible to compare performance with a solid section vertical fin. But without the computer data iit seems to fly in the cruise with a slatted fin of about 60% size of the cabbered profile design, and lighter. The hover performance can't really be judged.
The castoring vertical fin idea was a simple system linked into a similar mechanical design as the Agusta horizontal stabiliser of the A model and worked fine, The complexity appears to be no great headache as the MD Notars have adjustable VF's
Thank you for all your ideas.