Secondary keyword has been supported for a long time on HSRP groups. Shouldn't need an ARP entries.
Also make sure you need 12.2.8T. That is that you have new hardware that requires it, or need newer features in it. Otherwise, 12.2(10a) mainline is the better choice. Remember T train gets all the new features, and sometimes new bugs :-)
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...