As it turns out, it was calculating the Normals and Tangents for the mesh that was taking the most time. So I have added a Checkbox to the TeraTransfer blueprint that allows you to defer the calculation until you have finished placing the mesh.
By default it will be set to calculate these items (for the sake of convenience), but if you are going to have a very dense mesh for some reason (not usually the case), you can uncheck the box so that it will maintain better interactivity when placing the transfer. Either way, this is not really an issue for runtime, but more of a design time optimisation.