Tools Required: pliers, housing cutters, Allen key set, Torx T25 wrench, zip ties, 6' shift or brake housing, shift or brake cable, patience.
Step 1: remove the wheels & carefully secure the bike. Zip-tie the rear derailleur into its largest gear & disconnect the front derailleur cable; this will provide enough cable slack to remove the cable-routing plug with pliers.
Step 2: thread a cable down through the top driveside routing port near the headtube. Make sure that it comes out through the centre of the cable-routing plug by the bottom bracket without interfering with the shift cables.
Step 3: take a long piece of cable housing and thread it up through the seattube housing port and out of the top of the seattube.
Step 4: re-install the cable-routing plug by the BB. Slide the bottom end of the housing onto the cable and use the cable to guide the housing up and out of the top driveside routing port. Remove the cable from the housing.
***You should not have a piece of housing running into the headtube, out at the BB port, back into the bottom of the seattube, and out the top of the seattube.***
Step 5: thread the Reverb barb into the cable housing. Remove the Reverb remote from its hydraulic hose by unthreading the return speed knob and then unthreading the remote hose barb.
Step 6: push or thread the hydraulic hose onto the Reverb barb, carefully slide the connected hose & housing down through the seattube, and install the Reverb post into the frame. Slide the hose & housing up through the BB cable routing plug and out of the headtube port.
Step 7: after removing the barb from the hose & housing, carefully measure & cut the hose to length. Remember to adjust your saddle height & remote bar-position before cutting the hose. Thread the remote barb back into the hose & install the remote onto the bar.
***If the Reverb is not working properly after this procedure, you may need to bleed the system. Refer to the SRAM service documentation (sram.com/service/rockshox/50) for more info.***
That's it! Enjoy your stealth dropper post routing!