Awesome, thank you!Uplink ports can be use as normal switchports.
No cross-model stacking. Must be in same family. So 71xx, 72xx, 74xx, etc.
The only exception is if you are using them as 802.1br SPX extenders with a 76, 77, or 78 series as the CB, but that's apparently gone away in v9 of the firmware, possibly indicating EoL/discontinuation of 802.1br support.