On the Ignition side you can maybe tweak the Concurrency and CIP Connection Size settings on the driver but you’d probably need to adjust the overhead timeslice before doing this. If a connection size other than the default is going to work it will likely be <= 2000. I’d try 1000 to start and see if that helps at all.
Look at the mean response time versus the number of requests. Multiply. Divide by # of concurrent requests. The resulting # of milliseconds is the fastest pace your connection supports.
You might gain a bit by increasing concurrency, but if the bottleneck is in the PLC (likely), the response times will go up and you won’t really be going faster.
PLC bottlenecks can be mitigated by changing a continuous task to a periodic. In your case, I’d recommend a 10ms or 20ms period. Logix processors also have a setting for communications time slice. Increase that.