I did 25.17 a couple of years ago on my steel Favori with spinacci bars but that was on the fast V718 course. Generally I do 26-28 min rides on steel but the end of last season I trained a bit and did 23.50 (only 13 secs off my lifetime PB) on my aluminium Bianchi with tri-bars. Because of this I have 'invested' in a carbon TT bike (or at least the parts to build it!) in the hope of dipping below 23mins this year but with my recent illness, rotten weather etc. I can't see it happening. The trouble is that I am now at an age where another year older is another year slower not faster! After all, it will soon be 45 years since I first got inside the hour for a 25 - and that was definitely on steel!.
Today is the yesterday of tomorrow.