I think 5% is below market rate for what you are doing. By establishing 5% as the rate, you crowd out any local investment options which would need to charge above 5% (but not 60%). By making the subsidy non explicit, you make it even harder for local lenders to compete.
I don't know what a market rate for this kind of loan would be, but in the US, it would be more like 10%. Some kind of explicit discount due to social benefit or something like that, or marketing to launch a new business, or whatever, could make sense, but I really don't want to see the same situation where USAIS dumps free or subsidized goods and services and crowds out the local producer.
At the same time, sacrificing the (not yet extant) p2p lending sector in Kenya might be ok if it helps enough other businesses -- similarly communication and security being subsidized might be a net good.