Have you ever thought about having limits you can send to an individual? Even for people you have lent money in the past and successfully paid back?
I do not usually set limit. But when anyone ask for a loan and I review the post of the loan, merit, recent earning merit, activity, rank, trust, loan history then I decide whether I have to accept the loan or not. And if I think the borrower deserve lower number of loan then I also mention that via private message.