By now you should know the limitations, though, because many people with experience have repeated them here:
- An aerodynamic TT/tri position is highly individual, striking a balance between being aero and being sustainable for the individual. Deducing gains from highly trained individuals is hard, because they might be able to make a position work that is unsustainable for you.
- Usually, you cannot replicate a TT/tri position on a road bike with clip-on bars.
- If you can attain the same position and put deep wheels on a road bike, aero drag will be close. This makes sense as your body position contributes the majority of the drag.
- The faster you go, the more aero matters. The contribution of power you need to overcome aerodynamic drag grows with the third power in your speed.
- Most people aiming for an ambitious Iron Man finishing times are on dedicated tri bikes. That should tell you something.
- Even in the best circumstances, quantifying differences between kit and body position is extremely hard to impossible. Wind tunnel data is not representative of real life gains (laminar vs. turbulent flow). So even if you find data that quantifies differences in terms of watts, unless the gains are fairly large, I wouldn’t put too much stock in it. 5 W at 250 W is 2 %, i. e. roughly within the margin of error of many power meters these days.
Rather than talking in circles, you could tell us:
- Do you know what your tri/TT position is?
- Can you attain it on your road bike with clip-on bars?
- Do you have a disc rear wheel and a deep front wheel?
If the answer to the first two is no, you should really try to rent or loan a TT/tri bike to see what they feel like. If the answer to the last one is no, you should know that you are leaving some speed on the table, too.
To me the idea of clip-on bars is that you can use your road bike for two tasks. The more changes you have to make — and putting on an extreme stem, TT bars, TT shifters and brakes, etc. defeats that purpose.