I love the ubox designer, and especially the front panel designer! I have a few suggestions for enhancements:
1) Allow panel design for the rear panel as well.
2) Show the PCB as a cube, rather than a square, to show height for clearance checking.
3) make the PCB like panel holes, and allow multiples, such as a power supply and a function board, etc.
4) PCB could be a little smarter and allow a board size, and hole locations relative to the board. IE my board is 5X7 with holes at [0.2,0.2] .[ 4.8,0.2],[0.2,6.8],[126.96.36.199] holes are relatiive to board size.
Again, great design. Very well done!