Do clip on aero bars make sense?

He is kinda right.  But what he failed to tell you is that when you add the Aero bars that you will have to be refit.  Sometimes as simply as sliding your seat forward.  But your fit on a road bike and a road bike w/ Aerobars is different.

The whole compressing the diaphram thing, I don't buy.  More stress on the skeletal system, traps, etc..I'll buy that.

So, in short, switch to a Tri set up and mark those 'measurements'.  And then you can switch back and forth at will.

"compresses the diaphragm too much. Meaning that the aerodynamic benifits were more than offset by the stress on my cardiovascular system."

HA! what a load of fertilizer.

You may want to tweak your fit when adding clip-ons to a road bike, but even without doing that I am willing to bet that you'll still be faster in a tri/TT with the clip-ons than without.

I have a road bike with clip-on aerobars and my most comfortable position on my bike is in the aero position.   My legs especially seem to like that position as it allows me to use slightly different (and stronger) muscles.  My bike was refit when I got them.  I have the Profile ones that have the arm rests that flip up giving me the additional position for my hands.  I'd probably be even more comfortable on them if I was in better bike shape right now (Lake Placid is when? )

As far as the diaphram issue, that sounds like typical roadie B.S.  While there may be some increased pressure for lack of a better description, a lot of that depends on how aero you get in the bars, the seat position, your own flexibility and bike fitness.  But even in the drops you're going to have the increased stress.  The back especially would seem to be more stressed out in the aero position than the diaphram.  But to give you an idea of the benefits of aerobars, I did one 1/2 IM last year without the aerobars and one with.  While I was in better shape for the one with the bars, had I not had an unrelated mechanical problem that cost me a few minutes, I would have been 15+ minutes faster on a much harder course.