Sorry, this may be hard to answer without a pic, but a rep at one of the big 3 online tri retailers had no problem telling me what would and wouldn’t work. Here goes.
I ride a 54 dual, 78-79* with a 100mm stem, 250mm aerobars. I am 5’10" and after switching out the taller spacers on the bars for the smaller ones, the bend in the bars are pushing back against my palm so hard that I have to flex my wrist back to hold the grips or just rest my hands up on top of the shifters to relieve the discomfort (which puts my forearm at an angle that digs them into the back side of the armrests instead of flush with the pads.)
The rep said that based on my height and stem length there is NO WAY I could fit on anything larger than the 250’s I currently use, and that the 270’s would stretch me out too far. I feel like another 1-2cm would make a perfect fit.
Who’s got 'em, how tall are you & what size stem/bars do you use? I have a hard time believing that someone could make this determination without seeing/feeling what I do. Not to mention, the 250’s are listed as “small to medium” and at 5’10" I doubt I’m in the small range. Anyone?
My thoughts: 270’s and a hacksaw! gradually trim back until you are in the right place. I’ve always argued the shifters should be pretty much in your hand as you can shift when you need to without moving hands and therefore arm etc.
I bought some of these last week and also run a 10cm stem on 54cm bike at 79 degrees and they fit perfect. Unless you have really long arms I would think the large size would be…well too large. For what it is worth I am 5’9" so pretty close to you in size.
As for fit, I would go off of the bend at the elbows. That angle should be around 90-110 or you are supporting your weight with tricepts vs skeleton.
Seems to me that regardless of the numbers, if I’m in my most comfortable position and I have the bends pressing hard against my palms to the point of needing to flex my wrists, I need longer bars. We’re only talking about 2cm here anyway, going from the s/m to m/l.
The hacksaw idea may be a good way to go if the stock 270’s don’t get it done.
I’m 5’10.5", inseam roughly 32", and ride my P2 pretty steep - 82ish degrees. I am running either a 90mm or 100mm stem - can’t remember, but I have tried both, and 270mm clip-ons. They are a little long, the 250s seemed a little short. I’d rather have to reach a little bit for the shift levers and be able to choke up on the flats than to be jammed up.