The new tailfin attaches with pegs. I tried to make it collapsable, but there isn't space inside the leg (thus Yamatos problem with the tiny tailfins) I thought about trying to make it telescoping..but honestly that seemed outside the realm of my talents...so I sealed the hole, re-etched the panel lines, and made two small peg holes to attach it...this way I can remove them to transform it.
That's good! I bet ya you'll also fix the front landing gear too?