RE: single vs. dual conversion receivers
DSP can only work with the information that comes from the receiver itself. If you're running SC and there's a whole heap of noise or other RF on the image frequency then the DSP can only do so much.
If the signal on the image frequency is strong enough (compared to the signal from your transmitter) there's just no way any DSP system can extract the information that's been lost.
Besides which, why bother with SC you can buy a really good 6-channel full-range DC receiver with DSP that weighs just over a quarter ounce for as little as $17.