Kalki has not added or changed historical facts in SS. Mamalla @ Narasimhan's father was Mahendra varman. Pulikesin of Chalukya conquered him at Kanchi. Mamalla was vowing to avenge this.Father and son prepared for nearly 12 years to settle their score. Sivakami and Aayanachirpi are additions. Narasimha avenged the defeat of his father. In the end, in Kanchi,Narasimha was keeping Pandya Princess with him in the chariot - and not Sivakami. Historical facts not changed - including Paranchothi @ Siruthondar, Sundarar hyms - Kabaliga etc.
Vikraman wrote sequels to PS - 1. Vandhiyathevan Vaal and 2. Nadhipurathu Nayaki. We have discussed Vengaiyin maindhan also. Among majority of the Historical Novels - I opine - Kalki has taken more precaution not to step aside historical facts. I have great admiration for certain factors in PS :
1. Whether Uthamachola was really Uthama or otherwise. There is difference in opinion between Sastry and Sethuraman themselves. Kalki ensured not to get into this contraversy by describing a less herioc Maduranthaka till Crowning and Crowned Senthan Amudhan - who became Uthama?!
2. Who killed Aditya? Kalki switched off the lights in the Climax. There were Ravidasan & his brothers (Udayarkudi fame) Nandhini, Periya Pazhuvettarayar and VD. Inspite of Udayarkudi - Kalki gave the benefit of doubt to Ravidhasan. Above mentioned sequels of Vikraman were more of speculations.
3. Same way he did not allow Sivakami to ascend the throne of Pallava Kingdom - not to deviate from History.
Kalki must have done rearch twice: to write Pallavas and wrote Parthibankanavu and SS; to write PS and wrote 5 volumes of the same. With 14 wives lined up for Arulmozhi, Kalki should have found it difficult to describe Arulmozhi's romantic life and confined to one Vanathi. To pep he should have introuduced one Poonkuzhali! - who appears to be the modified version of Sivakami (less Dance.) As History proves, there is hell of difference between young Arulmozhi and much more serious and powerful Rajarajan.... (Kanthalurchalai - gangapadi - nulambabadi - ezham.. etc..) Mamalla had single Great Innings - like 6 sixers of Sobers! Kalki could afford to describe more of his romance!