Offered a deal on a 175 crank armed Ultegra to replace my crappy 172.5 FSA. Is the crank arm length really noticeable? I'll admit going in that I'm old and have cranky knees, and all my bikes are 172.5. Its a deal from a friend that gave him fits trying from 170, so although he's about giving it to me ($50) Id feel bad trying and flipping it if it didn't work. I'd ask to borrow it and buy it if it works, but it's about new and if I did that and it didn't work really wouldn't be "right" to hand them back.
Thoughts? (not on the deal, just whether it's a huge/noticeable change)