Michael, I dropped the thoughts of owning a shoulder plane when I realized that this was not a historic plane from the hand tool era. I look to this era for efficiency and quality in my work. I use wooden rabbet planes which which can take either a light cut or a heavy cut when making a rabbet. Also a fillister (fenced rabbet plane).
Before I bought a combination planes I had several plough planes that I made after Roubo's design. They make a groove of one width, one distance from the edge and use the depth of the groove as a stop. Although they are not versatile, like the universal plough, they make a very high quality groove. This open mortise design is particularly fast to make. If you want to make one I would have some additional comments.
Attachment 409044
We don't do much tongue plane work in furniture making. One use is for backing boards, which are generally rather thin. We don't use a tongue plane in frame and panel construction.