Somewhere between 3 and maybe 1000. Bots can vary the number of panels they have, so they can grow larger as time progresses. There'll need to be an upper bound just to keep things sane, but I imagine it'll be quite high. On the low side, it'll be somewhere between 3 and 6, depending on how the geometry works out for adding new panels. My best guess right now is either 3 or 6 as a minimum. Can't be smaller than a triangle, and hexagons can be formed in to triangles, chevrons, and hexagons, which mean it's a fairly versatile shape. So if triangles don't work out I'd probably aim for hexagons.