Hi Jeco,
The layout you have is not a problem. I have much more peripherals then you on my layout, and no problem.
The RS232 speed will not help to increase the reaction of the system. The "bottleneck" is the LZ100.
So some questions.
Which Lenz version are you running? is it 3.5?
Do you have the latest Chipset inside?
If so, you should update to WDP 8.5, as this version was modified to run much better with the Lenz feedback.
Switch of the Polling (Lenz verification) and the whole System should run smoothly.
If any further questions occure don't hesitate to contact me.
Regards Bernd