Single Loop Radiant

From reading on other discussions I now understand the concept of primary / secondary loops in a radiant system. But my system is small and I am looking to understand if a single loop will be Ok. I have a manifold with 4 loops of 1/2" Pex each about 250' long plus a 5th look about 150' long. From calculations I need to move about 0.6 GPM through each loop. I am purchasing a small wall mount boiler with about 2.5 GPM minimum flow required. Our current plan is to use a primary / secondary loop moving about 4 GPM through the boiler and a bit less through the manifold. I need to more carefully calculate the head loss through the manifold but using a single speed pump looks like about 3.2 GPM. Does it make sense to just use a single loop for this small system ??