[QUOTE=MKahrl;21095200]If you rarely use the smallest three cogs with a 50x34 you will use them even LESS often with a 52x36.[/qoute]
He said *bottom* three. Which I interpreted as the largest three, ie: the lowest gears. The smallest three are the top gears.
If you're doing 40 mph while going downhill you might consider going faster by stopping pedaling and going into an aerodynamic tuck.
Plenty of us live in areas where you will never hit 40mph in an aero tuck because the hills are not steep or long enough. But, with appropriate application of power (and tuck) you can get there. I know that race strategy says your power is best spent on the ascent, but when I'm out riding for fun I enjoy chasing a higher max speed. Always have since childhood.
To the OP, I'd only look at sizing up the chainrings if you are spinning out the top gear and are looking for more top speed though. I am in the same situation as you on the edge of going mid compact as well (already have the rings, just gotta install them). I've got plenty of low end on the gearing wand also don't usually use the lowest gears but it's the desire for a higher max that is pushing me to consider more teeth. I'm fine carrying around a few low gears for a bad day or a newfound steep hill, but only if they don't restrict my quest for top speed!