Use of agar agar as a substitute for gelatine

URGENT!

I am doing a favourite recipe for a vegetarian guest. It usually includes 12 grams of gelatine  to set 625 g of pureed strawberries, 3 oz sugar and 300ml of low-fat creme fraiche. This is poured on either a thin no-fat sponge base or fattening choc biscuit crumb base.

My question is, does anybody know how much Chinese agar agar to use as a substitute for the nasty gelatine? I have done some searching on Google but info is scarce. I would prefer to take advice from a real person who has used it!

If it's in powder form it doesn't take that much but if it's in the larger flake form it takes a little more. 

Here's what I found on google, hope it helps:

The Alinea reference cookbook calls for the use of agar agar at 0.5% by weight.

That is, if you want to gel 500ml (grams) of a liquid – you should use 2.5 grams of agar agar.

What you do…

1. Mix the agar agar with any liquid that you want to gel, and bring that liquid to a boil, whisking as you do so to dissolve the agar agar. Once the agar agar has dissolved completely, remove the liquid from the heat, and allow to cool. The liquid will remain liquid until it cools to 35 degrees Celsius, at which point it will begin to gel.
2. The gel will remain solid until it is heated again to 85 degrees Celsius.
3. You can also transform that liquid gel into a pudding by blending it until smooth.

Thank you very much for that info. Some references say that acidic liquids need more agar but I'll start with 5 grams and see what happens! I can always serve it as a soft mousse with a crumble topping if I don't get a complete set! I am going to give it a go this afternoon so fingers crossed.