I agree with you Bill, it could be very nice to add hole shapes by every contributors,
to make this tool easier for all users.
To be honest actually, I have no idea how to do that, but maybe the new Thingiverse project:http://www.makerbot.com/blog/2016/04/11/thingiverse-developer-program-invites-community-to-shape-the-future-of-3d-printing
we will have a way for that.
If you feel able to developpe something for, feel free to use the Ultimate box maker as you want.
I can only be happy to see this project growing with the all avalable hands.
For the community, by the community...
To finish, thanks a lot for your kind words, really pleasant to read.
Have a nice day my friend.