CO2 Cartridges!

So I went to my local REI looking for CO2 cartridges.  They had 16 gram and 20 gram options.  I normally get the 16 gram and I know they have plenty of "oomph" for my road bike but for some reason I want to buy the 20 gram cartridge (they were out).  I'm wondering if they would have enough air to "plump" the tire before I wrap it around the wheel, something I normally do with my mouth on the side of the road.  Here's 1 vote to standardize on 20 gram cartridges for road bikes, they're not just for 29er's anymore!

Shaving Legs vs. Aero Frame

These are the days when I wish I had a degree in physics!  I've been wondering a lot these days about aero advantage.  I'm 6'2" and at 195 pounds I make quite the "sail" when cruising along the flat.  I don't shave my arms, legs, or really anything other than my face.  However, the people to blow past me usually have two things: 1.) matching cycling clothes, 2.) shaved appendages.  I'll ignore them being 30 pounds lighter for the moment.  And it got me thinking, what gives you a more aero advantage?  Shaving those appendages or having an aero frame.  I figure hair and a fat frame both have to induce drag.

So which provides more of an advantage/disadvantage?

Would mountain biking help my road cycling?

I still can't quite figure it out.  I've gone to my share or mountain bike demo days and the legs/lungs don't seem to get a different workout.  It does make me wish that the road universe had an equivalent to the SRAM 1x11 drive train.  It also reinforces that I need to learn how to go downhill better.  I'm neither good at it on a road bike or a mountain bike.  The weird thing is that on a road bike I get nervous will all of the speed -- I get paranoid that my bike is going to slide out from under me.  On the mountain bike speed seems to be a good friend -- it's just about looking for weird things popping out of the ground (pesky roots and ruts).  I guess it worked by lungs a bit more but that wasn't based on cardio, just my nerves likely sending my heart rate up.

Stuck at 18 mph...

That's where I am, stuck at around 18 mph average speed when cycling along the coast.  I'm only 35, it's mostly flat, I'm not that bad, but I can't seem to get to that 20 mph level.  All I want to do is blame stoplights, stop signs, weird traffic patterns that happen when people going to the beach try to parallel park, etc.  But that's not the reason.  I'm just not sure if it's the legs or the lungs.  The big is fine, a Cannondale EVO isn't exactly the slowest or heaviest bike on the planet.  I've been looking around other blogs and evidently I have to learn to ride in the drops, do interval training, etc.  Maybe the"rest days" are going to have to become "stretching days".