laser add on to gantry mill

I have another thread about this but not sure it was the best place, anyway I added a 2.5w laser to my router and changed my preprocessor to use M3 Sxxxx to control intensity and it's all working quite well, BUT I noticed gaps and overburn in my images especially outline text. It seems that the laser is slow to turn on when XY moves leaving a gap and slow to turn off when starting a rapid move leaving a slight burn trail. (slow being a relative term)
Tommylight suggested upping the Z velocity and acceleration but that did not seem to help.
Can anyone suggest a fix (if possible) I don't know if its hardware (which is a crappy l-cheapo laser, bottom of even their line) or software, say in the trajectory planner.
I have a Mesa 5i25 (no 7i76 etc) driving a Gecko g540 so I have no access the hm2_5i25.0.pwmgen.00.pwm output as I would have in a stepconfig layout (or please correct me if I have this completely wrong)
Eric

You have another accessible PWM gen on the second 5I25 connector

I have ordered a cable to suit the P2 socket for this reason, but won't I have the same issue? how would I run that through motion.analog-out-00, would something like

net analogout motion.analog-out-00 => hm2_5i25.1.pwmgen.00.value
net spindle-enable => hm2_5i25.1.pwm.00.enable

and use G68 E1 Q1 in the pre processor work ??

any guidance appreciated
Eric

I think what tommylight was suggesting was to use the z position to set the PWM value
rather than spindle, since the z value would be synchronized with motion and spindle speeds are not

Thanks I'll re read tommylights files but I'm still not grasping how to use the mesa card pwmgen as opposed to the software one, I need an example (if I'm not asking too much) on how to use the mesa card pwmgen output with motion.analog-00-out.
apologies for being so dim.
my limited understanding is that the software generated pwmgen has a pwmgen.0.pwm output but the mesa card one does not. I haven't seen one mentioned anywhere so please correct me as required.
Eric

If you are using a G540, the first hardware PWMgen (pwmgen.00) will connect
to the G540s spindle analog circuit but the second pwmgen (pwmgen.01)
will connect to the unused 5I25 expansion connector.