Hi Diagnosid!
Just to follow up from Davids post – I did IM70.3 Aix en Provence in September, which has approx. 1200m of climbing over 3 climbs. I managed to get a fair bit of training in my specific phase on mountains, and it does help. However, I did use Best Bike Split to work out how hard I could and should push on the hills. Basically I pushed as hard as I could, whilst keeping an eye on my splits and normalized power, so that I didn’t over do it for the run…..
Good luck!
Gareth