1k per 4x5 will be sweet. Better dispersion if you run the bulb parallel to the short sides.

In the discussion above, I was rec'ing that you use 4 x 1k for the 10'x10'space, just to be clear.

This is about the same footprint per light.

I've had good luck packing 'em in as tight as 4 per square foot- no veg time at all, tiny cuts ( about 3"). To start out, though, I'd try around 1 per square foot, or 20 in a 4x5- you want to know how the strain reacts before you squeeze them in any tighter. SOG takes a little dialing time.

Whatever you've got that tends to minimal branching and a single dominant cola is a good place to start. It's much easier to SOG from cuts, if you can- variance is the enemy.