Simple with the following generalizations. Start with the IBO speed for your bow.

Subtract 10 fps for every inch of draw length you are below the 30 inch "test standard".

Next subtract approximately 1 fps for every 3-4 grains of arrow weight you are above the IBO "test standard" arrow weight of 350 grains. (a552 grain arrow would cost you about50-67 fps)

Next add or subtract approximately 1.75 fps for every pound of draw weigth you are eitherover or under, respectively, the IBO "test standard" weight of 70 pounds. In your case that means you lose approximately26 fps.

Lastly, subtract approximately 4-5 fps for every string accessory you have installed on the bow...peep sight, string silencers, string loop, etc...

Then take all of those numbers and subtract/add them to your IBO speed rating to determine a fair estimate as to your speed.