I tried all kinds of springs, rubber bands of different length and strengths, etc. I switched to the new flags with the holes in them and they seem to work better for some reason for me. I have the regular springs in the 2nd hole from top on the boards and can get good results with cranks on the lower flag holes a d good results with 40tt by just moving the the spring towards the top of the flags.

I think the new flags are only a few bucks each