Peter, an F2D plane can turn around a 1.8m(6ft) continuous loops.  Hardly anyone does that in competition so is around 1.5m(5ft) radius in stretched out figure eights,

For F2B

Peter, the numbers I get are for a nominal 20.75m line lenght(68ft) and a nominal 3.7m(12ft) turn diameter are:
Flight circle= 130.25m(68ft)
The bottom side and the vertical sides are 16.3m
The flat side length is 8.9m(29.2ft)

The 45deg flight circle is nominally 92.1m, the loop width is 11.5m(37.75ft.) including the turns.
The level flight length is 4.1m(13.5ft).

A 3.7m turn radius is extremely good.  A more realistic figure is 4m, or even 4.5m.

This leaves unsaid what 45deg. means.  Is it a latitude(level flight) or a great circle path.  The great circle path looks straight to the pilot.  The difference between latitude and great circle paths in 4+meters may not even be noticeable in only a few meters.

Thanks for doing a difficult job.