I brewed the second version of my Helles on Monday, and it's happily fermenting away at 18c (64.4f). 5 gal, 1.043 (should have been 1.048, but this is my first brew in my new & bigger pot and got my volume calcs wrong), 5.43 mash ph, and 1 pack of W-34/70 rehydrated.
Will raise temp to 21c...