Doing some calliper measurements and a few photos to explain:
Minimum distance between Source Audio pedals is using the metal connecters.
20mm between the sides of the two Pedal's shell or 11mm between the jack bezels:
View attachment 4792585
Or in a Stereo context. These work well because the side walls of the Source Audio pedals are flat and vertical, unlike say a Hammond enclosure which is tapered:
View attachment 4792619
Next best are the Warwick Rockboard flat patch cables. 25mm between the sides of the pedal shells or 16mm between the jack bezels:
View attachment 4792587
If you Stagger the pedals, you get 16mm between the shell sidewalls and 9mm between the bezels:
View attachment 4792592
However, your pedals are vertically staggered by 9mm.
If you connecting Source Audio pedals with 5 pin Din midi cables, using the Rockboard Flat Midi Cables and Patch cables is currently the most space efficient. As seen between my EQ2 and Collider, 25mm between the casing walls or 16mm between the jack bezels:
View attachment 4792617
I hope this helps!