I agree, certain popular tri bikes don’t give you the option of a second bottle
Some comments:
I would press/question the manufacturers of these bikes on why they do this, given the information out there that the frame mounted bottles are not that big a deal from an aero perspective
Typically those bikes have one mount on the downtube and in all but an Ironman race, a large bottle on the down tube is likly all you will need - assuming you can use the drinks supplied out on the course during the bike. I have done a number of 1/2 IM races in this manner.
A handlebar mounted bottle such as a jet-stream is an option for a second bottle, but personally I don’t like negative impact on the bike handling of adding this much weight to this area of the bike.
I used to have a Saddle wing and used it on both my road and tri-bike beause I always had trouble getting bottles around my knees. I dropped bottles and found myself swerving around trying to look down to find the cages right underneath me. The saddle wing was easy, and I didn’t have to look anywhere to get to it, just reach behind my lower back. That said, I use a profile aero bottle between my aero bars now, mostly because I don’t have to reach anywhere at all. I keep an extra bottle on my frame and if I dry out I just dump it into the aero bottle. The only problem I had was that the straw they provided was kinf of sharp and if I was sipping and hit a little bump I cut my lip, so I put a bite valve from cammleback on there and now it works great.
