China  has authorized two banks to invest 3.5 billion US dollars of their clients' money overseas, bringing total approvals so far under a scheme to promote capital outflows to 8.3 billion US dollars, Reuters reported.   The foreign exchange regulator said that it had granted a quota of 2.0 billion US dollars to China Construction Bank Corp. and a quota of 1.5 billion US dollars to Bank of Communications. Since the country's foreign exchange reserves have surged to a world-high 941 billion US dollars, many economists have advocated greater outflows of foreign exchange as an escape valve to release some of the upward pressure on the yuan, said Reuters. Still, the size of the initial allotments has surprised some analysts because quotas granted under QFII, a mirror-image programme for inbound portfolio investment, have typically been just 100 million to 300 million US dollars. Analysts reckon QDII funds are most likely to flow first to Hong Kong's market, bolstering stocks listed there.