not easy at all! I mean you could shorten them, but then you lose the bit at the end.. I have seen some 3" ones which would be ideal but they don't come in stainless... Might have to accept that for the better fit.
I was going to use your method, but I found the 5/8 to 3/4 and thought i'd try that. I will most likely need a washer on there too.. Or I might just put the brass bush that comes with the shank on the front and use that. At least then I can ensure a tight fit with no interaction with the twisty bit.
I'm going Nukataps too - I think in worst case scenario, If I can't find suitable shanks I'll just add more threaded nipples to bring out the tap a bit. But would prefer 3" shanks if I can find them in stainless.