I am sorry but I can't participate, I slipped to accept the offer.

Thanks for the invite.
I do enjoy a challenge, but I should point out that although you have given a comprehensive brief, from a design point of view this project will need a lot of work. Perhaps you should think about upping your payment a little (or at least guaranteeing the payment) and also extending your deadline a few days.
You may be surprised at the participation.

regards