The K-1 Scout was from the infancy of the hobby.
The reason why the fins were so thick was to prevent damage to the fins.

You have to remember, this is a tumble recovery rocket, the specual engine hook kept the engine with the rocket.

The motor would shift causing it to tumble, therefore "tumble recovery".

I can't go into details right now, but, something sprcial was planned for Estes 50th, you fill in the blanks.