Within normal arrow weight ranges, your KE won't change much (a few tenths of a lb-ft or so). With your original #'s I came up with 66lb-ft of KE. If I assume your going to get the same energy I come up with 233fps with your 550gr arrow. Your energy will go up slightly actually with the heavier arrow so you might get slightly more than this ... which puts you right at 235fps! I think I heard that somewhere before?

... Shockwave