Try playing round-the-head forehand shots, otherwise there's not much you can do, the best thing to try would be to mix longline and crosscourt dropshots so that he has to keep guessing where the shuttles going to fly.

You're saying he doesn't play net shots, so the only thing he does from that area is clear I suppose. That's a huge advantage and also very easy to exploit, just move back a little further after you played a drop shot and then immediately prepare to hit an overhead. Even if you're smashes aren't that good, you can win many points with constant variation as Matthew said, play punch clears, drop shots and slice smashes so he has to keep guessing and then you should win if he has such big weaknesses.

So, in short:

-Play as much net as possible and then prepare immediately for your overhead shot, seeing as he doesn't return with a net shot.

-Mix your shots but just don't give him time in the rear court to use his big smashes.

-After the first set or so, check how he responds to your new tactics and adapt accordingly (in case he does play more at the net for example, you should move your base position a bit more towards the net).