I'm really surprised how much the concrete has shifted under this thing. I'm going to have to add shim plates as now the leveling bolts are maxed out in the front and min in the back. It almost feels like I'm reading something wrong, but the floor has dropped more than a half an inch over ~2 feet.
Nice work... i have a nearly identical machine to yours and have been contemplating replacing the rpc it came with, and going the vfd route...
You are probably aware of this but in general you would rarely if ever start up the lathe with the spindle engaged. I see you noted that the clutch / brake may need adjustment. I would sort that out right away.. the 1500 manual is fairly detailed about this.. and the folks in kalamazoo still have small parts etc...
One of the best things about using a vfd is the ability to soft start the motor, i.e a 5 - 10 second accel up to full speed removes a lot stress from the system.. especially when coupled with a vari drive system which may have been shut down at max or some high speed .
If and when i get around to setting mine up I would for sure use the soft start , but let the motor / vari drive coast to stop.. i.e. 0 decel time..
The clausing has a pretty good speed selection but i can see a need for occasionally fine tuning a speed or slowing down to 20 rpm or so... really the best of both worlds..
Hard to imagine what is going on with your concrete.. short of checking the concrete with a level.. i am pretty impressed with the way clausing set up the mounting feet.. note that once leveled accurately the machine will take a while to stabilize... and i would check it again after a week and then again in a month or so.. and generally once or twice a year or prior to doing any precise work..