Nice job on the chip containment. You may want to get rid of that mat though. We tossed away hundreds of that style at our shop in lieu of going with solid mats. The mats with the holes will hold all of your chips, and when you pick it up to clean it, the chips are still stuck in the mat and all around it.
Once I get around to it, I think I am going to go with a VFD like you have, so may have some questions. I run a phase converter now and my Lagun is a belt drive. With one arm that I can't raise up, I can't change my speeds to where I want at times and have to get the wife to help me. I'd really like to eliminate having to do that.
Just curious, when you say you are going to drip feed a program to your mill. Any reason for that? Once you have your program coded, you should be able to send the complete program over to the mill without drip feeding it. The Prototrak 2 axis should be more than enough to hold a large program. That way it frees up the computer for other things while the mill is running. I don't know how long you've had your ProtoTrak, but Southwestern Industries have online manuals you can download if you don't have one for yours. If you haven't done it, look in your manual about calibrating the ProtoTrak "X" & "Y" movements. I found on the ones we had, that it was good to do it a couple times a years. Over a period of 6 months I found that ours would be out up to .005 in each axis. Not a lot for as much as ours were ran, but still enough to get into trouble with some things.
One other thing to you may want to do....if you open up the panel box on the side of your mill, you will see a disk drive in there. In it, there is a 3 1/2" floppy. You need to back that disk up. What's bad with the older retrofits, they use the 3 1/2" floppy drive and disk to run the mill. The disk is a boot disk and has to remain in the drive for the mill to run. Hardly anyone has a 3 1/2" drive anymore. Every computer today has a CD drive and USB ports but no 3 1/2". Another thing too, if you don't have a 3 1/2" drive, if you get a chance, shop CL or go to some computer store and get an old computer that has one and set the 3 1/2" drive back, just in case the one in your mill ever goes bad. We lost ours to power surges. We had (2) 2 axis mills in the toolroom and had to replace the 3 1/2" drive in each mill. Southwestern Industries want $600 for the drive. It is no different nor is it anything special than the 3 1/2" drive in any older computer.
If you ever have any questions about the ProtoTrak, let me know and I'll help you out all I can. We had the (2) 2 axis ProtoTraks that were retrofitted on our mills, then we bought a new 3 axis called a QuikCell. We were having some problems with some of our programs so I worked closely with Southwestern resolving the issues and found out how really simple the hardware is on the mills and what to look out for.
Hopefully before long, I'll have the same setup as you do now. I looked at a 2 axis retrofit on a BP that I'm almost positive I'm going to get, once the guy replaces one of the servos, which I found out that the servo is a proprietary part of Southwesterns that cost $1500 for a replacement. Ouch!!!!!