75 Ohm BNC cable

@jasonbourne71    Reflection coming from the end of the cable (if any) can deform original edge affecting timing.  For 1.5m cable reflection from the end of the cable comes back in 15ns  (5ns/m x 1.5m x 2).  Even the very beginning of transition (knee) will come back later than 12.5ns  (middle of typical 25ns transition), where most likely level change is recognized (threshold),  It is all guessing game, since transition time and propagation time in cable can vary.  I would go even for 2m, but if you are already short (29 inches)  cutting it very short might reduce reflections.
There are also chances that characteristic impedance is matched perfectly and there is no reflection at all.

The cable is constructed in such a manner that any modifications you carry out will compromise the build and suffer a loss in audio quality.

"It includes connections inside of electronics on both ends, so it would be safe to go with less than 12 inches to avoid reflections. “ 

Circuits, Tx/Rx, I designed, match driver and receiver impedances to cable, thus no reflections on both ends, length of cable becomes irrelevant..

"why do you need to cut original cable? additional 15inch cable will not hurt your clock or other digital signal much.. if you  are DIY person, there are very good cables to terminate by yourself w/ BNC..."

Because the original cable only 0.7 m and longer but Chord Mscaler and TT2 are stacked together so I don't really need long cables.