first of all, thank you for this mod, very very, VERY usefull. Basically after the first try, it became indispensable. This message is in reaction to what you said : "However I would welcome feed back from other users - would it be better if this aspect of its functionality was developed somehow, and if so how do you suggest I make it work?" to begin with, how about you change the "USAGE" section of your post, because Usage: To set the CoM position - add the PWB Fuel Balancer to your craft remove any stages that will not be present when using RCS turn on the CoM indicator mouse over the PWB Fuel Balancer part press 'M' to set the CoM position. press 'D' to display the CoM position doesn't work with a one staged spacecraft, maybe the way it really works is a bit difficult to explain... try us ! you say : "it only starts moving fuel around once the stage that it is in has become active (more specificly it depends how far up the stack you attach the unit)" When does a stage become "active" ? when you say "how far up the stack" do you mean on the arborescence of the vessel .cfg file ? or physically how far up, which doesn't really give a clue when you are building a rover for example. as for suggestions, I don't know, would it be possible to make this work with an "activate mass error calculation" button on the pwb fuel balancer control contextual right click menu ? thank you again for sharing your mod, and for being interested in the feed back please be clement with my english as it is not my mother tongue. LE TEINTURIER