So I found some Lowboy plans on the forum that appeared pretty good, but low and behold, I have some conflicting maths and am now unsure if I made an error or not. The plan I followed shows an 805mm radius... but not sure that is correct. Hopefully someone can chime in and help. Below is the attached side profile. Any help or advice is appreciated.

Use a 1"x2" to create a giant compass.

- Draw a line down the center of the 1"x2".

- On that line, mark the center of the pencil hole and two small nail holes 805mm and 816mm from the center of the pencil hole.

- Drill the pencil and small nail holes.

Draw an 816mm arc from the center point of each 11 mm radius circle (blue) -- 816mm = desired final 805mm arc + the 11mm circle.

From the point where those two arcs overlap (green) draw an 805mm arc.

If you did it right, the 805mm arc will reach right to the edge of the 11mm circles.

Scott