Ok that makes a bit of sense
I'm going to post a power curve for cooling Vs cutting efficiency later this evening but you should be looking at something like the following:
3mm Laser Ply 65 Power 25 Speed
3mm Cast acrylic 80 power 22 Speed
3.2mm Medite MDF 70 power 22 speed
This allows for the tube being at mean life power levels and nominal water cooling with a temp around 22 to 25 degrees.
Get it cold and things change A LOT!
Mines running on 80watt tube @ 3.2mm MDF 65 Power 35 speed and is cutting reliably so far.Will post back later when I have more info
best wishes
Dave