The proliferation of interest-only hybrid adjustable-rate mortgages in the subprime market isn’t hurting MBS investors – at least not yet – researchers at Friedman Billings Ramsey say in a new report. “So far, the average [hybrid ARM] poses no incremental risk over an average conventional adjustable-rate mortgage loan to capital markets participants,” wrote Michael Youngblood, a managing director in FBR’s asset-backed research group.