Slice Rear Hyrdation - which cages?

I’m having some issues with the rear hydration setup on my slice. I’m using the one that came with the bike and I’m on my second set of cages and I’m still launching bottles.

I tried some elite cages originally and only launched when the bottles were half full. I switched to arundel (plastic) at the recommendation of my LBS and launched both bottles this morning - which were full.

While this is probably a good way to get the person drafting behind me to back off, I’d like to find a solution that works.

Any thoughts and suggestions appreciated.

I am using a Profile Design carbon rear holder with PD bottle cages… On rough roads I loop an elastic band and it holds them in. Smooth roads no ejected bottles.
http://www.competitivecyclist.com/profile-design-rmc-carbon-fiber-rear-mount-with-kage
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