Yeah that has been true for me too. I think its probably better to error on the lighter side rather than the heavy side of things. It will also keep the progression going a little longer. Today for example when I did my bench drop sets I went down from 120kgs to 90 kgs which is 75% and I could barely get 3 x 3. It was a close grip but I don't think it should have dropped that much? I'm thinking of going down to 70% next week. Yeah just keep tinkering with it, I do think 5lb increases on the drop sets is the best idea though. However the most important lift should be the max effort ones so I wouldn't drop a rep of those to get the full set of 5s in, those are just icing. And down the road there may also be some merit in doing something similar to the 5/3/1 program if you really want to practice the higher rep schemes with heavier loads. Interval training is so much better when you have a group to run with and keep you motivated.