Are you trying to block rain or are you trying to be aerodynamic?
For rain, a front fairing doesn't do much unless you can get one where you can tuck your head behind while also going fast enough that the rain blows over you. In Japan, I've ridden mom bikes with fairings and can say that they do zilch for rain until you're going at least 20kph or higher.
For aerodynamics, fairings can also act like a sail which can lead to considerable instability.
One significantly nice thing on a recumbent is that the fairing will prevent you from eating bugs. Since you're more upright, there is a tendency to consume more than on a road bike where you are facing downwards.
If you're planning on an extended trip at high speed (such as a cross-country run) it might be worth it, but otherwise you may find them to be a net disadvantage. Only one way to know though -- try it!
p.s. There have been crowdfunded attempts at full fairings but they weren't funded -- I think most people don't think it worth putting something on full-time for something they'd only use on rainy days and which might also block your vision (note lack of windshield wipers). Even bicyclists in Seattle just use rain gear.