Chick Problem- adding a day old to a clutch of week olds under a hen?

[Th0r]

Ok so here is the situation:
3x one week old chicks + 1x day old chick + one mama hen =?

I had 8 eggs in the incubator and only 3 hatched..
But wait.... I had 2 more, put in the incubator a week later.... (long story .. we had a roo and wanted him to fertilize our silkie hen.. he did but we had to re-home him so we wanted to incubate all the eggs we could)

Only 3 hatched (incubator went flaky and got "cool" at the end of the hatch 5 died after lockdown.

Now the 3 are a week old under mama and doing well- they are out from under her and pecking / scratching etc..
One of the 2 other eggs hatched today.

We dont really have a brooder.

Is there any way I can slip the chick under her and it will survive. I know she will adopt it. she is like that as a mama. BUT the others are so mobile at a week and I dont know if she will just sit on the #4 while the other are out and about in their pen.

So should I try putting #4 under her or should I leave it in the incubator for a couple days with food and water and the top propped open for ventilation?

Any ideas / suggestions.

Thanks.
Thor

 

[SunHwaKwon]

My chicks hatched 4/29 under my hens. I gave her a couple chicks from my neighbor that had hatched 4/22 and took the remaining eggs and put them in the incubator. One hatched 5/2, then another 5/7. Each time, I added the new chick right under the wing of mama with no issues. I now have another chirping in the egg and I'm hoping I can get her to take this one too (I'm not sure why the eggs are so staggered- I think the other hens kept adding to the clutch while she was sitting). So, my point is that, depending on the hen, you can add more chicks. I think it helps that I actually have two hens co-mothering so neither knows how to keep track. I don't know if it would go differently with a single hen. I also think making sure they are dried out and fluffy to match the rest and tucking them under the wing helps too.
I was worried about this last one being able to keep up with the rest but by day 2 it is able to hang with the others even with the oldest already trying to practice flying. They know to run under a wing if they get cold right from the start.

 

[Th0r]

FYI
Everything seems to be working out ok.

All 4 chicks were outside today running around together and #4 seems to be keeping up.