When it come to choosing the right limb design, all the books I've read leaves out the "when". They talk about back profiles dictating the braced profiles, but more or less skip "when" these particular limb designs are appropriate. I think first, you have to consider side profile before deciding on limb designs of either pyramid, parallel or somewhere in between. The right design for draw length, bow weight, handle design, arrow weight, reflex/deflex , and back deformities (or not) need to be considered into the "when".
Start you a list of "considerations" before you ever begin. First and fore most, know your wood's MC to minimize set...........Art