I'de recommend when investing the rest of your money to stay away from A grade it returns only about 5% and B grade returns almost 7% and that is without any filtering. Since you're new I'de recommend going to nsrplatform.com create an account and play with their backtesting filters to optimize note selection for what you are comfortable with. Since you're already heavily invested in A grade loans it would be better to invest in a breakdown something like 10% A, 30% B, 50% C, 10% D, or 10% A, 40% B, 40% C, 10% D.