Could one as the owner not temporarily "sell" a share in the aeroplane to someone else, and then buy it back?
I looked at "renting out" and came to the conclusion that the way to do this was to make the "renter" a member of the group, and add them to the insurance policy in the same way as a normal member (subject to them paying any additional premium).
Then sell them a share temporarily for an amount equal to the insurance excess (plus any additional premium due) and block time. After they have sucessfully completed their flight, I'd "buy" back their share for the same as the insurance excess "deposit".
Likewise I have a few select people who I'd be happy to let "borrow" my aeroplane (for costs). As such I'd name them on the insurance policy.