On the axle sprocket, a higher (numerically) toothed sprocket will achieve a slower top speed at a given rpm.
If it runs out of steam at the end, you need to go smaller (numerically).
If it's a dog off the corner, and you have not achieved what you deem as peak rpm at the end, go larger (numerically).
When I used 700's, I had sprockets from 42 tooth to 54 tooth, in 2 tooth increments.
On my Mod-x, I found a 2 tooth rear sprocket change, typically would yield a 400 rpm difference, but that may not hold true for you.
