I am not proud about my knowledge in optics.
Many years ago I bought a D2, it came with 2 ¾” cone. I used it with 150mm lens for good time, until having bought from Harry Taylor a 4 ½” cone.
What did I do (without knowing) using the 2 ¾ “ cone ? Image distortion or what ?
Thanks for consultation.

Sergio Caetano