Although Neil makes a superb fixture for checkering the front strap, there are enough dink factors present to make checkering a miserable job.
Most front straps are not uniform. If you use a radius gauge on one, you will get the point rapidly. Not only are radii ad-lib, but different manufacturers use entirely different shapes and locations.
So, Neil's fixture is not to blame for lopsided work, it is the original radius.
Uniformity of machine checkering is predicated on a uniform dimension between the surface of the outside frontstrap radius and the interior magazine well radius. If this varies even a few thousandths, the work will not be uniform. Some professionals advise welding and re-shaping or in some cases, re-contouring.
Ask yourself this: Do you really NEED a checkered frontstrap that will anchor your grip and not allow a slight shift of position during a draw?
The original GOld Cup pistols had a perfect compromise: Frontstrap grooving. Gripping down will anchor the position solidly, while a lighter grip will allow a shift.
Before you spend $500 plus bucks on a checkering fixture, measure all of the aftermarket frames and compare the dimensions. Fixtures such as Neil's are usually based on the blueprint dimensions of (idealized) Colt frames. And, incidentally, many professional shooters hate sharp points and will blunt them off before firing the pistol, anyway. Perfect rows of perfectly pointed checkering is an obcession with certain pistolsmiths. I wish them lotsa luck and continue to produce workable, practical grooved frontstraps that meet with approval from most shooters. (If you really can't live without checkering, all you have to do is cut cross lines to turn grooving into checkering.)
If you want a simpler solution, learn to hand checker. Better still, avoid it entirely and apply grooves or skateboard tape or a Wilson insert.