Here's an expandable travel pedalboard that I did for a client back in New York. The total size was 18" x 16".
The client wanted the most compact footprint as possible with the ability to expand out for volume pedals and delays off of the left side of the pedalboard (Vertex Modified FV500 Volume pedal and Vertex Modified DL-4), and additional overdrives, fuzzes, and uni-vibe sounds off of the right side. The board can still be used "as-is" if desired.
Voodoo Lab Pedal Power 2+
1) Vertex Dual Buffer (dual input/output buffers), Effects Break-Out (a separate SEND/RETURN to wired pedals off of the pedalboard after the overdrive pedals and before the modulation pedals).
2) Effects Break Out - underneath Tuner (a separate SEND/RETURN to wire out of the left side of the rig a volume pedal and delay pedal that feeds back into the pedalboard).
Interface (input buffer), Sonic Research Turbo Tuner, Lovepedal Tchula, Maxon SD-9, Rockett Blue Note, RC Booster, (Effects Break-Out #1, inside interface), Vertex Landau Modified Arion Chorus, Retro-Sonic Chorus, Analogman Chorus, Rockett Josh Smith Dual Tremolo, (Effects Break-Out #2, underneath Tuner), Interface (output buffer)