I should work at work, instead of researching hypothetical bike builds:

http://www.bikeforums.net/archive/in.../t-433254.html

Looks like the IRD 11-34 10 speed cassette works with shimano mtb rear derailleurs, but works better with older XT or XTR ones than the newer ones.

Various people saying they got it to work vs. didn't - santana 11-34 cassettes seem less finicky than the IRD ones...

But I think at some point it's going to come down to, how patient of a mechanic do you have...

I know the BF tells me a lot of times what I want to do doesn't work... and gives up and does something else if I let him. Then when he wants it to work on his bike, magically he fiddles with things long enough to make it work. Other times I have to just pulling up webpage links going "it says so right here it'll work" and he'll roll his eyes and keep at it to prove me wrong, until he makes it work.

I could of course get better at tuning stuff myself, but I haven't gotten to the point where I can make finicky stuff work yet.