The method posted in post #2 was the method I had originally used - I did the HTC unlock, then followed the directions. I was able to flash a ROM, which is great - the ROM I'm using is snappier than stock, and the battery life is significantly better, but I was hoping to be able to flash custom kernels as well. If I can't, it's not the biggest deal in the world (pretty much the definition of 1st world problems), but it's frustrating. Step by step, I had done exactly what that said to do.
Ah well...not to be with this phone, unless someone figures out another way to get around the 1.50 hboot. Thanks, guys.