Coincidentally I've been trying clip-on aero bars on my '89 Centurion Ironman. The old school Scott aero bars were sheer torture, no way to make those fit.
I just tried a set of Profile Carbon Stryke, from a TT/tri bike with cracked frame that I'm stripping for parts. MUCH better. Even without a proper contemporary TT/tri bike geometry and fit, it's a huge improvement. I just raised the seat post/saddle about 3/4", put on a Cobb V-FLow and scooted the saddle as far forward as it would go on the original seat post (really needs a zero setback or other proper seat post).
Did an hour on the indoor trainer, then ventured outdoors for a 20 mile test ride. Only did a couple of minutes at a time on the aero bars, mostly flat sections including some moderate descents and climbs. My balance needs work but I can see why some folks like these for long distance rides, even if they aren't doing time trials.
And I could use slightly longer bar extensions. The Profile extensions weren't quite long enough to let me park my arms closer to the elbow on the arm rests, and get full extension of my forearms. No big deal on my short test ride, but I'd prefer a better fit for longer distance.
On the negative side:
- The balance is terrible. No way around that even with lightweight aero bars. I won't be carving any curves at high speed in the wind.
- You may need much wider regular drops or bullhorns. I prefer 40cm drops and the comfortable Profile armrests prevent riding the tops, hinder the hoods, but the drops are okay. I'd need either 44cm drops, or bullhorns which set much lower but offer only a single hand position which would get tiresome over long distance.
- It takes a different approach. I needed less power to get the same speed, but found it difficult to generate more power and go faster. Probably just takes practice, and a proper fit would help. Or just get a TT/tri bike that's already set up for this.
If you decide to stick with drops it'd probably be better to switch to aluminum drop bars and not worry about crushing the carbon fiber bars. FSA Omega compact drops are cheap and good. I might try a set of Gossamer too, which have a slightly flattened top.
If I stick with a hybrid road/TT setup I may switch to the Dura Ace bar end shifters that came with the TT/tri bike on the Profile Carbon Stryke aero bar. Not sure I'll keep this setup on the Ironman, it was just an experiment to see if I could tolerate it at all.