Lemon sour

[Coastie]

I’ve got a Philly Sour in the fermenter about 4 days now, I was thinking of adding some fresh lemons/juice as I’ve got an overflowing lemon tree out the back. I’ve juiced some and have the juice freezing now. Would I just add the juice or some rind too or even while slices? Would I need to pasteurise it too? Lastly I was thinking of adding it on the last day before kegging, would that be a good time to do it?
Thanks everyone!