A couple of people have asked this now, so I thought I should address the question in the FAQ's.
To add another project to the book will increase the cost substantially, no matter what kind of project - it would add a minimum of 40 pages (increasing the base cost of the book by a lot) and involve developing, and testing a new pattern and then making three variants and having them professionally photographed. The additional cost would also include additional fees for proofreading and photographing the tutorials, paying a model to come for fittings and to three shoots, the cost of materials including hardware/fabric/embellishment for 3 different corsets(particularly costly and time consuming if I were to make 3 drag corsets), and higher postage costs for a larger/heavier book after so many people have already paid the current correct amount for postage. Kickstarter fees also need to be accounted for.
In order to not make a loss on this project, I would need to raise a further £3300 at this stage to even cover the basic costs of adding a brand new project, without paying myself anything for the extra work. To pay myself a fair wage for 150+ hours of extra work, it would take closer to a further £5500.
I was able to include the winged overbust because as a stretch goal, because I already have the pattern and two sets of photographs - hopefully you can see why a fifth project is not feasible.