Thrift institutions would have a slightly easier time qualifying certain low-downpayment mortgages for the most liberal risk-capital treatment under a proposed rule drafted by the Office of Thrift Supervision. Thrifts now can count mortgages with loan-to-value ratios of 80 percent or less in a risk classification for which they hold half the normal 8 percent capital requirement. Loans with higher LTV ratios may also qualify for this risk classification if they carry private mortgage insurance