A minor flurry of issuance of mortgage-backed bonds by non-bank lenders may rebut suggestions debt investors have had their fill of this asset class."It does not currently appear feasible to significantly increase the capacity of RMBS markets," the Reserve Bank of Australia wrote in the Financial Stability Review on Friday."This is because the investor base for such instruments is relatively narrow andsecuring new investors has been a prolonged and challenging task."Bragging that the reverse is true, La Trobe Financial on Friday detailed demand and pricing on its Capital Markets Trust 2019-1, its first such financing for this year."This program has seen both continued support from repeat investors and a progressively widening investor base with each transaction," for an RMBS pool of A$3.65 billion, its CEO Greg O'Neill said."We welcome 3 new large global investors to our already 33 investor-strong RMBS program and are delighted by the strong interest we have received on this transaction both offshore and domestically."Pepper Group made much the same point in an announcement last week on pricing for its I-Prime 2019-1 Securitisation."This transaction was particularly well supported by our deep, diversified and growing global investor base, who invested in both the Australian and US dollar notes," Paul Byrne, Pepper's group treasurer, said.Pepper and La Trobe are big wheels in the sector often mislabelled as "shadow banks".Non-bank mortgage lenders, a more sedate term, accounted for less than 5 per cent of outstanding housing credit, the RBA said in last week's FSR."Non-bank residential mortgage lending is estimated to have grown by roughly 15 per centper annum over recent years, well above growth in lending by banks.