Richard: thanks for revealing the term “capsule aperture” to me. I may well contact Russ and suggest that he consider adding them to APT.
For only slightly trailed images (major/minor axis < 2, say) an elliptical aperture works very well – as measured by comparing the results for untrailed subs and circular apertures with their trailed counterparts of the same field and a carefully chosen elliptical aperture. If you examine some of my entries in the VSS database you will find some examples of elliptical aperture photometry.