[13] RV Tauri variables often have somewhat irregular light curves, both in amplitude and period, but R Scuti is extreme.

The period-luminosity relation for type II Cepheids suggests a luminosity of 9300 L☉, similar to the spectrophotometric derivation at 9400 L☉.

[8] An extreme post-AGB star would be expected to show measurable secular changes in its temperature and period over the time that R Scuti has been closely observed.

Instead a relatively low mass loss rate with an extended cool atmosphere and fairly constant temperature and period of variation is seen.

One suggestion is that R Scuti is still a thermally pulsing AGB star, consistent with calculated levels of mass loss.