For tight indoor tracks, the best frame shape is usually a true X, or at least something very close to it. The reason is simple: it tends to give you a more balanced feel in roll and pitch, which matters a lot when you are making quick snap turns, diving through small gaps, and correcting line mistakes in a short amount of time. On indoor tracks, especially in gyms or school halls where the layout is compact, that predictable response often matters more than top-end speed.
A stretched X can feel a little more efficient in forward flight and can be nice if the track has longer straights, but in very cramped layouts it may feel less nimble in rapid direction changes. It can also make the quad feel slightly less “square” in the air, which some pilots notice when trying to thread a sequence of tight gates back-to-back. That said, a lot depends on how the frame is designed overall, not just the shape on paper. Arm stiffness, motor placement, weight distribution, and even stack height all change the way the quad behaves.
If your indoor track is really technical, I would lean toward a compact true X with short overall wheelbase and good front-to-back balance. That usually gives a cleaner corner entry and exits that feel more consistent. For example, a 3-inch or light 3.5-inch build with a tight X layout often feels sharper than a longer stretched frame even if both are built from similar carbon and electronics. If the track is more open, a slightly stretched X can be a good compromise because it can carry speed a bit better without feeling too twitchy.
Another thing people overlook is prop clearance and crash durability. Indoors, you are clipping gates, walls, and sometimes the floor more often than outdoors. A frame with protected arms and a compact center section can save you a lot of broken carbon. Heavier frames may feel stable, but if you are chasing fast lap times on short courses, extra weight usually hurts more than it helps. You want something that stops and redirects quickly, not something that glides wide through every turn.
My honest advice is to choose based on the kind of indoor track you fly most often. If it is tight and technical, go true X first. If you regularly get a couple of longer straights and want a little more carry, try a mild stretched X. Either way, keep the build light, the center of gravity clean, and the arms stiff enough that the quad does not feel mushy when you punch out of corners. If you have a chance, compare two similar builds back to back, because the difference becomes obvious fast once you start linking gates at race pace.
