With the exception of the 3Rensho, Colnago and the Alan, I run half-step on everything (with 7 cogs or less). It is the only way to go. Do not worry much about cross-chaining the granny gear. By the time you get 4-cogs into it, you ought to be able to jump to the middle ring.

Watch the cog spacing on the IRD 6-speed. My calcs give a 14-16-19-23-27-32 as the best combination for a 14-32, but I am not sure that is what the IRD has.

BTW- most older derailleurs will do ok with a 30-50 front end, especially Suntours, Falcons, and the longer-caged Shimano's. Newer ones generally will not because they have molded cages to work with specific chainring combinations which do not include half-step arrangements.