Fat Bird laid another egg!

That's two this year. Big deal you may think. She's coming up to 9 years old and my concern, with good reason is like many hens she develops peritonitis. If she's laying an egg every now and then and is otherwise healthy this is a good sign.
Tackle from Tribe 1 has been sitting on a clutch of six eggs in the nest box in my house. Ruffles who is the grandmother of Tackle started laying her eggs in this nest box four days ago. Ruffles decided she was going to sit last night much to Tackles disgust. Basically Ruffles hustled Tackle off the eggs. But, while Tackle would not dream of having a go at grandmother Ruffles she did sort of wedge herself alongside. Ruffles did peck her halfheartedly a few times but Tackle persisted and this afternoon the pair of them were wedged in the box together. My problem is, Ruffles developed a limp last time she sat and hatched from leg strain. I dare not let her sit again in case she compounds the problem.
Last night and tonight I've picked her off the eggs and put her on a perch in the tribes coop. There are eight days left to go. So, Ruffles does the day shift and Tackle the night. I might just end up with a double mum hatch.