If you really need to form small d-loops based off of limited back cast room, you really should be thinking of using a very short (20 foot) Skagit shooting head along with your preferred running/shooting line (100 feet) plus whatever tip you need (10 feet).
The Skagit style head is the easiest to learn with. A lot of grain mass is concentrated in such a short head which means easier d-loop management.
The three most popular shorter Skagit heads for switch rods are Rio Skagit Short, Airflo Skagit Compact, and Beulah Tonic.
Edit: If you want to get a better understanding for Spey lines and heads, read this article by Simon Gawesworth. It may refer to Rio lines and heads, but the concepts work for all makes and models.