Pls don't hate me but isn't it more practical to attach the horn side to the subframe like you did with the compressors.
Less stress on the tail cowl re daily riding plastic fatigue and greater convenience re taking cowl on/ off as no need to disconnect the air lines or navigate two lumpy bumps (the horns) up past around two other lumpy bumps (the compressors)?
I slide my tail on from the back while keeping the free ends slightly wider apart until sliding the rear tailight end into place. Granted your tail light is now attached to you tail so your process will be slightly different anyway.
You've done such a great job I don't wish to rain on your parade, just thinking of the practicalities (albeit we don't usually take our tails off very often).
No hating here! Good point. First airhorn on first build was a one piece system and placed it between my front forks.
However, on closer inspection I really have no fears concerning load on undertail.... Essentially the load is carried by two bolts that connect to rear of subframe. The key to handling the stress loads is part
11 steel washer with a neck. Sooooo, no worries! The compressor lies on the small ledge near part 6,7 on both sides. The ledge provides a natural stop. With a bolt going through plastic and heavy duty tie wrap(provided) to further secure it. So again no worries mate!