Okay, late reply.
I ended up with:
1 manky grapefruit that the possums hadn't eaten, from the tree in the backyard
2 oranges, already zested for another recipe and
2-3 lemons also previously zested
I think that's right, I just kept adding until I got the right weight.
(Honestly, my sister has a fruit bowl full of zested fruit!!!)
It was a kerfuffle, because here I was doubling the recipe and completely forgot that the recipes in the book at 'capacity'. SO, I had to pour the mixture in and out as I got it all done.
In the end, it was delish!!!!! And I used the same sugar as the recipe.