BTW in case you are looking at helments and "want to try", do consider Rudy project's Wingdream. Really solid and super comfy, not sure if placebo but together with a bottle in your jersey, the effect maciam like nearly could feel it. I have not run mine under hot weather but night time ok. It has lots of space at the sides and front so specs users ok wont hit the specs like others would (eg those short tail cramped ones like Wing, Codatronca, Adwatt, Procen etc).
But since SG T100 is so undulating, so not sure if the aero is that needed or not. But if you want to play aero a bit during training and "look pro", this is it.
Like Hambini's 2.5SFF rule, ie 190W and 175W or > 15w difference then you can feel it. I think this helmet + water bottle in front is around this ballpark even at 35kmh. Maciam like 30-35mm wheels vs 88mm wheels or possibly even trispoke front and full disk rear. No joke. And you tell me how much $$$, effort and time you need to spend for 88mm race wheels / trispoke + disk....and then you swap in/out for races and training.
(T100 banned front water bottle down jersey in around Apr 2024 but seriously for age groupers, nearly impossible to enforce and DNF you one lah, esp for duathlon where it is so bloody dark lol...like the 12m no drafting rule also, how to fully enforce)
Expensive, but bloody worth it, and it might work in SG weather esp if you have heat trained simply coz of the small vents + space around your head. Just get 1 solid one, that works, and be done with it for the next decade. For T100 duathlon it definitely would work, just that the triathlon a bit hot (Actually very hot) for the triathlon.
Unfortunately big size is sold out, i have the large size. Very popular helmet, i think many age groupers and pros know it really works.
https://www.tradeinn.com/bikeinn/en/rudy-project-wingdream-time-trial-helmet/141481217/p