Hi Richard,
When I make my standard cams, with 8 litres of standard raw milk, I expect a yield of around 1.25kg cheese. My early cheeses ended up high in moisture, and yield increased to 1.5kg or more, but with the subsequent loss of shelf life.
I assume you have added some cream to get a "double cream" brie, so your yield will be higher. So from 16 litres of milk I would estimate you should get nearly 3kg of double cream Brie. By the look of your heifers, you have a bit more than that, and it is almost certainly water!
I would target around 1kg for my bries, so 3 hoops for 16 litres of milk would suffice, as long as the moisture was normal.
How are they looking now, after being de hopped? Have they slumped at all?