I have a 2015 TI, and use a Davis Spar Fly with a solution (maybe not the best) that seems to work for:
1) Attaching to the mast end without affecting the furling up of the sail near the top, or permanently altering the mast head.
I used the round metal base mounting option, with all three screws attaching the base to a small wood block.
The small wood block fits over the top of the mast, and only extends about 1 1/4" down the mast head.
I simply hold the wood block over the mast head with one hand, then pull two zip-ties onto the block and mast head with the other.
I "sacrifice" the zip ties each time, using two fresh ties to hold the wood block base to the top of the mast each time.
Both the zip-ties go through notches I chiseled into the edges of the wood, recessed so as not to allow them to slip up or down.
The top zip tie goes around only one of the plastic in the very end of the mast.
The bottom zip goes under the straps holding the sail onto the top of the mast.
When done, I cut both zip-ties (one use only) with a small knife.
2) Carrying the Davis Spar Fly wind vane around without damaging it.
This is a challenge, as at least one person has mentioned.
My solution: carry the Davis Spar Fly upside down in a cardboard box big enough to hold the wind vane (around 18" X 10" deep).
I hang the Davis Spar Fly upside down, with the round metal base and the small wood block extending above the box when closed, and tape it shut on each side with painter's tape, which is easily removed and even reused a few times.
I remove the sail from its cover, then take the wind vane out of its box, and carefully remove it when done.
Admin: Edited to image URLs (was page URLs)