Real-world range vs. payload on electric trucks

We've been running our electric Class 6 box trucks for roughly six months now. The spec sheet says 200 miles, but the moment we load them to 80 percent capacity, we're seeing closer to 110 miles in mixed urban delivery. It's been a real adjustment for our route planning. How are other fleets handling the payload-range trade-off? We're now considering shifting lighter freight to the EVs and reserving diesel for the heavy loads, but that feels like it defeats the purpose. Also, our depot charger is only 60 kW, so opportunity charging mid-route is not really an option. Curious if others are seeing similar numbers with loaded box trucks and what fleet economics you're using to justify the operational constraints beyond just fuel savings.