Here's what I'd do for the strut speed brakes: the nose is a no brainer, simply put a partial door that opens in front of the strut as a big, "flat-to-the-airstream" panel. For the mains, fashion some flat panels that also attach to the struts and are retracted when the gear is up, yet big, out-in-the-stream panels when the gear is down. The only disadvantage that I can see is that your nose may not lock down if you are low on air, but just put a scrub strip up there and it'll be just fine.