Investment Dar Co., a shareholder in luxury British carmaker Aston Martin, is asking creditors to take a 50 percent writedown on the Kuwaiti company's debt as it seeks to meet repayments after defaulting on a loan three years ago, according to three people familiar with the matter. Under the optional plan, creditors will receive a cash payment totaling 5.7 percent of their outstanding debt and a portion of a new Islamic loan equal to about 44 percent of their current exposure, the people said, asking not to be identified as details aren't public. Investment Dar's stake in Aston Martin and real estate holdings will be among assets backing the new credit facility, according to the people.