I now have setup presets to send activate on or off via CC 15 to the first H9 on midi channel 1 and the second H9 via CC16 and midi channel 2. These are the "channels" that correspond to the switches 1 and 2 on the IA3.
For tap tempo I currently use the CC11 which corresponds to FS1 sending CC number 20 on channel 1. I see no way to also use FS1 to control tap tempo on the second H9. I could of course send a tap tempo command to the second H9 on one of the other available IAs but that's not via using FS1 repeatedly like the tap tempo on the device itself.