So, no need for a 4B on the HF/mids when using a 4B for bass?
Hi, you could BUT in the ST series the clip lights appear to come on early and I think in a 2 way sytem 4+4 is a workable option but the two I mention above I feel better options, I have run those systems.
The 4B + 4B would allow vertical bi amp - But any voice changes between amps then becomes an issue, If they were close serial number pair and much newer I would be more happy with that route.
So many things to consider.......
As always these are my opinions and not rules! But are based on testing done in my own little world.