Realizing that I can essentially stick a RS910 junction box into a round extension had me wondering whether it may be possible to pair my base bar (Missile Evo + the spacers) with extensions that have round cross-sections through out. The stock Missile Evo extensions are round at the tip (so that shifters can be mounted) but transition into an ovalized cross-section where they are secured to the base bar (via the spacers). I'm wondering it may be possible to swap other extensions (and still attach to the Missile Evo basebar via the spacers).

One complicating factor is that the mounting hardware I currently haveused is ovalized, so the extensions I'm looking at have to be able to receive M6 bolts (the basebar has slots that matches the countersunk on M6 bolts). The other is that the extensions have to have apertures near the mounting point, so I can thread the Di2 cables therethrough (and via the spacers and into the basebar). Anyone knows anything that might work here?

Alternatively, could the innards of RS910 be trimmed down so that it would fit within an oval cross-section with minor axis length of ~13 mm? My guess is no, as the RS910 has a circular cross-section of 22 mm, and most of the circular cross-section is filled, so to speak.