Odd chainring combinations with SRAM Rival front shifter
 

The main question: Is it possible to have "good" front shifts using a SRAM Rival front shifter with a 40/24 chainring combination in a 10-speed drivetrain? If so, which combination of chainrings and deraillerur would work?

Here are some supplementary details which may be relevant:

I have a Sugino AT triple, which I'd like to set up with 40/24 chainrings using the middle/inner positions (and a bashguard on the outside). The drivetrain will be 10-speed with a 12-28 in rear. I've not yet purchased the chainrings. I've mostly been considering either Sugino or T.A. chainrings (such as on http://sheldonbrown.com/harris/chainrings/110.html), though I'm open to suggestions. I also have an older XT M735 triple derailleur, but I realize this may not be ideal for this set up. In case chainline could at at all come into play, I'll be running a 122.5 Shimano UN55 bottom bracket, which I believe will give me around a 45mm chainline with this crankset.

I've read that, for instance, at least some Shimano shifters are somewhat dependent on the proprietary ramps and pins, though I've read it is a bit less of an issue with a double. I also realize 40 is fairly small for the "big" chainring. I'm not looking for race performance, but at the same time I don't want the shifting to be a source of constant frustration.

Thanks in advance for any advice or experience. Let me know if I've left out any important details.

I suspect that you might have the best results using a Sram mtn FD, setting the height as if there were a 48 or 50t in the outer position. That will locate the shift ramp shaped into the cage's inner plate at the right height for shifting up off the 24t. The FD won't know or care that there's no outer ring there, but make sure that the dummy ring or bashguard on the outside is small enough for the cage to clear it.