Mine are rootbound in 7g cloth pots and they're much smaller plants. Fabric pots don't prevent plants from getting rootbound, they postpone it. They also make for "better" rootbinding (?) by filling the pot with feeder roots rather than the huge roots wrapping around the inside edge of solid pots.
You could try coring at various angles and depths (just not all the way to the bottom) with barbecue skewers or heavy gauge wire.
You could try coring at various angles and depths (just not all the way to the bottom) with barbecue skewers or heavy gauge wire.