A little advice sought:
I am 6 feet tall, weigh about 170 and am on a 56 cervelo p2 with a 90mm
stem. I am using Zipp vuka aerobars. I used to be on a size 54 P2 but needed lots ofspacers and upturned stem. The 56 is great in terms of height/stack, but I like a shorter reach. So thinking of shortening the reach by using an 80mm stem. Is this safe? Too short? Make the bike too twitchy? What do you think?
I have used stems shorter than that, and once you get used to the steering change it isn’t bad. If your aerobar pads are even with the basebar you’d be fine, but if they are closer to the saddle it gets iffy for anyone behind you.
Without seeing a pic of you in riding position or knowing anything else, I’d say 80 is usually OK; below 70 is kind of the general “too short” threshold.
Of course the other obvious variable is moving the saddle forward… how set are you on where it is now?
using a fizik arione tri 2 and it is as forward as it will go. the aerobar pads are even with basebar.
I’m 5’10, short torso and ride a 54cm P2. I think they have me fitted on a 70mm stem. Don’t feel that handling is negatively effected.
I’m 6"2 and use a 120mm stem on a 58 P2, with adamo saddle all the way up. If you are sure your arm position is correct in the aero position, get the shorter stem. Put a picture up for better ideas.