I've been using baby clippies for a long time now! You are right!
They work great!
Here is my purple malabrigo bed jacket, sleeve all clipped into place, ready to seam:
Here they are, holding the cables in perfect alignment for the shoulder seaming:
The clippies are also great for 'try ons'. In this photo, I had to see exactly how far down the shoulders would 'drop' in order to determine the right sleeve length! I hate mountain gorilla sleeves!