Joe thanks for the additional pics of the duck in the up position but I will stick with my opinion that for my taste it is too tall. But you can put me down for a shorter version. I think you have done a fantastic job with the shape and overall appearance but that shape and curve blending will be different when it is shorter.
To my taste the taller version would be great for a track car but for a street car looks too " ricer " . No offense to those that like it . If you produce both sizes the free market will choose which version is a better seller. How sturdy is the install ? Would you recommend the end user to use automotive adhesive in addition to the OEM rivets/screws ?
One last thought, not to be a safety nazi but does the tall ducktail impede the vision to the upper brake light when in the raised position ? In this litigous society we live in don't put yourself in a position to be sued because your ducktail blocked a brake light. I am looking forward to seeing pics of the shorter version.