lol. some really bizarre advice being doled out here. im not sure what makes less sense, 1k-10k series resistor, BIG supply caps, or that fuss over the diode which is really an excellent way to drop voltage. fortunately there are a couple guys here with feet on the ground. unfortunately noobs cant always tell whos who.
personally i doubt that for hobby use 4 new alkaline would be a problem. it dont make a lot of sense though. current will be extremely high, non-standard voltage for interfacing, and little advantage over 3 cells, 4 nimh, or a single lithium. powering off a single cell (regardless of type) with cheepo ebay 50 cent boost module is another way to guarantee exactly 5v.