Clip-on aero bars?

Adding clip-ons can help, but it's a compromise and can introduce problems.

I've used Profile Design T2+ in the past, which I liked, but you have to consider the fit to your body and bike geometry as to which one will work the best.

here's a couple of articles to check out..

http://triathlon.competitor.com/2012/06/gear-tech/adding-clip-on-aerobars-to-your-road-bike_54972

http://www.active.com/triathlon/Articles/Aero_on_a_budget__Transform_your_current_ride_into_a_race-day_workhorse

I x2 the Profile Design T2+.  Moving down onto areo bars, will move you center of mass forward.  This alter bike geometry and handleing.  Also gripping the bar ends changes how reactive the steering inputs are converted into direction changes.  That said some bikes are effected more by adding areo bars than others.

I would try it.  Being down low reduces drag, alot and that translates into free speed.

Aero clearly has it's greatest advantage at greatest speeds.  I question whether bolt on aero bars are as aero as using the drops.  A TT Bike has no relation to a road bike with clip ons.

Using your formulas below there is a 1 second/km advantage going from drops to aerobars. 40 sec. in a 40km TT. Pro cyclists use a full TT rig because those seconds are huge in the pro TT circuit where the gap between first and last may only be seconds. Yes, more speed increases drag, but the time savings in a 5 hour IM bike ride vs a 30-45 min. sprint do bare out. This is triathlon, not pro TT. So while having a good aero set up is important, most, especially MOP's will get greater benefit from clip ons in longer distances while saving something for the run.

Short and lightweight, definitely, but not too short.

My first set of aerobars with a Profile Design aluminum hoop (the classic shape) with flip-up armrests. Two problems. First, it made my bike horribly nose heavy and darty.  I hated out the bike handled with that thing. Second, while flip-up armrests sounded like a good idea in practice they were a hassle to use.  I couldn't hop in and out of aero if I always had to maneuver my elbow to get into it.  Sort of hard to describe, but if you're on the drops and want to go aero, I had to sit way up, maneuver each elbow into place up and inside, over the armrest to push it down, and then back to aero.  Hassle!

Next, I overcorrected with a pair of short bars so short they weren't useful as aerobars.  They had no armrests per se, instead they used pads wrapped around the handlebars.  Well, that wasn't very comfortable.  And they were too short to get my hands in the right position.

The third set was a carbon version of the Jammer GT.  This is the aluminum set:

http://www.profile-design.com/profile-design/products/aerobars/aluminum-aerobars/jammer-gt.html

These were ideal.  Short, lightweight, very adjustable, solid armrests.  Perfect!

http://www.profile-design.com/profile-design/products/aerobars/carbon-aerobars/carbon-stryke.html

These work very well for me on my road bike. I like them so much that I am thinking about putting them on my tri bike which has the s bend bars which are not as comfortable for me.

This.

I went with a pair of shorty bars for my first two seasons.  I didn't make any other adjustments from my road position as I didn't want to mess with that but rather add in another position.

I started with the short bars but found that I have long forearms and when my elbows were over the pads to support my weight then my hands were too far forward to hold the bars comfortably.  The t3s have a great range of adjustments and are much more comfortable for me.

Here's interesting comparo test data using same pro cyclist with road bike +/- clip on aerobars vs TT set up:

http://www.cyclingnews.com/features/how-aero-is-aero

Basically found a full TT rig vs road bike (drops) saved roughly 25% power at 40kph.  Prob a bit lower % power savings (20%?) @ 30kph.  Over half that power savings was seen for road bike with clip on aerobars, so there is real a speed advantage in addition to the comfort factor of extra hand positions.

This is only my third tri season so I just went through the same thing.  I bought the cheapest profile design ones I could find on the web...they were about $90 from Amazon and save me about $10 from the local bike store.  I wished I had spent a few more dollars as mine are a little short and not as good as I would like them to be.

My suggestion is to buy them from a local bike store and ask them to install them etc and see if you can weasel an unpaid bike fit into the deal.  Just tell them you want to get up on the bike and see how the handles fit.