I just mounted my brand new Corsa 25s on a pair of Ambrosio Excellights. They measure exactly 23.8mm. So I wouldn't worry too much about the aerodynamic penalty to be honest. I assume working on your riding position, tucking your elbows etc would help you a lot more in that respect.
thank's - 23,8 a little less than what i had hoped for - perhaps they will meassure wider on Open Pro's, i'll post when i get mine.
My Corsa 25 arrived to today, they too measure only 23,8mm on a OpenPro ceramic rim - quite a difference to my old Pro2 25 which measures a whopping 26,4mm. a difference of minus 2,6mm. In regards the height of the tire the difference is 2,1mm.
Mounting without any tools was easy although initial fitting of the inner tube was annoying. The tire fits very secure to the OpenPro rims. I kind of hope that the kevlar beard over time will move up a little on the rims and increase the volume of the tire.
Like most 25mm clinchers they undermeassure quite a bit, just like the 25mm Conti GP4000 and Vredenstein Fortezza TriComp i have tried out durring the past 7 years. In fact the only true 25 i've found was the Krylion Carbon (Never mounted Pro3's but they should be smilier to Krylion Carbon).
I'll see if 23,8mm is big enough for me, otherwise i'd might use the Corsa's as front only and get something larger like Vittoria Open Pave or Challenge Parighi-Roubaix for the rear.
The profile of the Corsa's is very close to the profile of a classic tubular, much more than the late 90th's Vittoria Open CX, Open Extreme and Open All Weather i rode back then (last time i rode handmade open tubulars).
Looking forward for the snow to melt and try them out... and se if they are as smooth as the Open Extreme 21mm i rode 15 years ago (smoothest rolling clincher i've tried)