Toby,

Sorry it took so long to get back to you. I have tested it on several different make and model bows. Both a 60 and 70 pound peak draw weight comparison as well as one bow set at 60 and 70 pounds. There is a much more pronounced difference with the latter but there is still a difference in speed with the former as well.

However, the actual speed difference varies significantly from model to model and also depending on the grains per pound of draw weight ratio being used. Some bows might only see a speed difference of 2-3 fps whereas I have shot others that varied by 8-9 fps (60 and 70 lb peak draw weight comparison). My suggestion of 7 fps was the easiest to actually prove using the normal generalizations, however, 4-5 fps would be more of the average of what I have found.