Look at the cute spaceplane at 175 km orbit with 4,975 m/s of delta-V
Goodbye Minmus stops.
Besides the monopropellant tanks in the front, I also lowered the flow priority for the small Mk2 Lf tanks so that they'll keep the CoM near the front. It was a struggle to fly this monster to the KSC, but I managed... and voila.
One thing I would like fixed is the control point on the carrier once I detach the spaceplane. Since its cockpit is the designated root part, my screen focuses on that part until I switch to the carrier. However, when I do, it is being controlled from the underside docking port.
I would like to fix that issue at the SPH, but it's not as important as actually flying this thing. If fixing it at the SPH isn't possible, a user could just hit "Control from here" on the probe core.
Mars-Bound Hokie's post in Spaceplane Carrier Help, Please. was marked as the answer