hat size does the i4 chainguard go up to?
The thing I like about a 54 is that in 1st at a stand still there is no need to shift the drailler. Shifting twicw on the ihg and your off. Then fine tune shifting with the 9 speed. If I stop in 27th I just change down on the ihg and off again. Works so slickly and fast freom brifters. With the 56 its a little over gearedand I need to change on both more often. I love my close ratio cassette, so I am currently running the 54.

I am running a 11_21 casseTte, as my bike is set up as a fast road bike with kojacks,bullbars,clipin peddles, and brifters. I find gearing fine for hills.
My sash gold bike has a 11-19. 7 speed. I could do with a smaller gog or more spread.