C-types like Bennu and Ryugu are rubbly and soft. Even if we see them here, their origin is the grey zone; once Earth-trojan or Cruithne, their orbits are inclined and eccentric, making for a delta-V headache. At the 1 AU range where actually reachable, our main options are stony.
The Atíra class is difficult to see from Earth as they run close to daylight, like Venus; if stony, as many are, they might reflect light, but unless of Atira's massive volume, we don't see much more than a bright dot. So, I'll use higher-AU S-types for proxy. Like Didymus, which we've sent missions at.
Didymus is unrepresentative in one other way as helps us. Didymus is an oblate spheroid. That means it is composed like a fluid - and as not a differentiated body, it is made of rubble. Hence also why it's got a moon, from ejecta. Contrast solid and irregular Apophis: Didymus looks porous at 2400 ±300. And it is spinning already; we could spin it more.
Didymus has major radius 425m × minor 310m. This volume is ~2.34e8 m3, subRyugu. Let's start smaller. Posit a rock the physical size and shape of Bennu, but stony: 2023 EL, maybe. The size is 6.15e7 but density is 2400 for 1.5e11 kg.
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