The way the unit seemed to bounce around even in Jim’s video did not inspire confidence to me for the versions attaching from under the saddle or rails, especially knowing it is 3D printed (even if a higher end SLS or MJF print).
My training buddy got one of the EZgains for his Cervelo a month ago - it broke on the first training ride. Not the attachment the saddle interface part, but the top part where the bottle cage interfaces.
I think it Georgia Taylor-Brown had issues with it at T100 London, no?
On the ST’s main page on the article for the bikes of the top 15 pros in Nice, I noticed that Kristian Høgenhaug’s EZgains is hanging by a thread there with only one mounting screw left holding it.
(Now the top part here does appear intact.. so unless the part the front screw threads into under the saddle failed, it’s might be just an installation error and the screw got lose during the ride).
The newer version (v2) EZgains have for the Wove saddle that KH was running in Nice should be less critical though (solid connection, small lever) than their usual configuration. So again, maybe the front screw was just not tight enough.
I am one of those that rigged my own setup on the Wove saddle when I saw Jim’s results for the side-by-side 2 bottle BTS setup….
… in which I was able to integrate a transition hook under the saddle as well: solves the issue of trying to pass the bike under the transition rack (with the extra height of the BTS setup).
Lighter than the EZgains setup, 107g to be exact. So Saddle + BTS hardware (before adding cages) is still lighter than most stand alone saddles.
It is lower profile as well, easier to swing my leg above it during mounting. Although maybe less aero than when the bottles sits higher?
(more details in the Wove Saddles post
Wove saddles - #210 by spocket )
While there are 3d printed parts (spacer and transition hook), none of them are structural and the setup is super sturdy and rigid: I would trust my setup over any of the EZ gains configuration going from the brackets under the saddle.
I actually made 2 kits for the Wove guys a couple weeks ago.
I have yet to do aero testing on the side-by-side BTS setup compared to a single bottle or double bottle in vertical arrangements.
If only 1-2 watts differences, my aerosensor, opportunities (weather) and testing skills might not be good enough to really differentiate them with confidence.
That being said, if the 3 setups are really close, there would be value in knowing you can run 2 BTS bottles instead of 1 with very little aero penalties if any.
And if vertical vs side-by-side is also tight, I do find it easier to handle the setup with 2 side-by-side bottles on top of the saddle as opposed to dealing with the bottle under the saddle, and I can use the transition hook for efficient racking in transition.
Anyway, if I get to test in the coming weeks before it gets too cold here, I will post the results.
I mean, if someone can confirm they just 3d print these, I’m going to lock myself in a room and start modelling/3d printing alternatives at affordable prices 
150g total weight means a material cost of €2,40, plus a few cents for nuts and bolts.
