Buyer who opts for dual-agency contract with seller's broker cannot complain about the agent's failure to protect him

The VanHellemonts agreed to buy a $1.6 million dollar estate from the McManamons in Oakland County.  They used as their agent the McManamon's broker, and signed a dual-agency disclosure agreement.  The deal slowly fell apart and the VanHellemonts were sued for damages or specific performance.  They sued their realtor for malpractice, arguing that the agent should have written the buy-sell to protect them more fully:  in particular, they alleged the document should have called for the loss of their $35,000 earnest money deposit, rather than a $500,000 penalty, in the event that they did not close on the purchase.  The Court concluded that the VanHellemonts gave up their fiduciary duty claim against the realtor when they agreed to the dual-agency relationship.