This is something I made for placing RCS thrusters in the right positions in the first try without having to go back and forth between the VAB and the hacked gravity launchpad.
RCSBuildAid supports blizzy78's toolbar, if you have it installed, enable RSCBuildAid from there. If you don't have the toolbar installed then you enable RCSBuildAid by enabling the center of mass marker. Once you enable the plugin you should see RCSBuildAid's window show up. Press the RCS button or any of the translation flight control keys, the "hnijkl" keys, and then you should see something like this:
Cyan arrows represents thruster forces, the green arrow represents the translation motion (or thrust). The red arrow represents the torque force in your vessel, if you have a red arrow then your ship will rotate when trying to translate in docking mode. So all you have to do is place your RCS thrusters in a way that eliminates this force. The red CoM marker is the dry center of mass (DCoM) which represents the center of mass of your vessel when it doesn't have any fuel (liquid fuel, oxidizer or mono-propellant).
Check the imgur album for some examples
This plugin is incompatible with KerbCom Avionics. If you're interested in using both plugins then I suggest to poke ZRM about it.
Sources are in the zip file and in github.
Licensed under LGPLv3.
Code:This program is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this program. If not, see <http://www.gnu.org/licenses/>.