This layout is better, as you you can locate two holes with the same reference.
It's also much easier to discern where the two lines intersect.
How to locate the holes for the bearings in the upper and lower platens.
You can save some time by clamping the upper and lower platens together, and drill all the holes in one go.
Close enough method:
1. Make sure you have accurately set your lengths.
2. Draw a circle with a radius of 173.2.
3. Choose a starting point on the circle for the first hole location.
4. Draw an arc with a radius of 300 mm, where the arc crosses the Dia 173.2 circle is the center of one of the holes for the Roton lead screw.
If you want to get precise by doing it by hand do the following.
1. Make sure you have accurately set your lengths. Use a loop (magnifying glass) to set your tools.
2. Coat the location of the holes with epoxy, mix in a black filler (ground up pencil lead will work).
3. Place a piece of saran wrap over the epoxy, and weight it down with a piece of glass.
4. After the epoxy has dried layout the holes.
5. Use an eye loop and by hand and with an awl press into the cross hairs.
6. Review your work, if it does not look like it is perfectly centered with your aided eye (loop), push the center prick mark back on center.
7. Drill with a very small drill a hole into the prick mark, this will be your pilot and guide for the next drill.
8. Step drill until you reach the final hole size.
Practice first on a piece of scrap material until you are comfortable. Practice on holes separated by 5.0 inches, that way you can verify your work with calipers. Leave the drill bit in the hole and use it as a pin to measure the center to center distance.
Your millage may vary, but I think if you have never done this before that you should be able to get your holes laid out to within.005" to .015", if your layout lengths are correct.