Logope,
Your idea to design the tree trunk in the shape of "FF" is most creative. While I like the idea of including the "FF" in the design, in this instance, it appears to take away from the idea of a bonsai tree. One of the things I like about the bonai tree is that the trunk is not straight. The curves, are to me, what gives the tree its own character.
Thanks for your submission.
Respectfully,