We just went through this in rally because CARS now requires double-strap mounting mechanisms.
I did a group buy of 2.5LB Amerex double strap brackets from AZE (
https://www.azeperformance.com/) earlier in the year. They're made for 3" Bottles but can be very slightly modified to fit ~3 1/8" bottles. Have two in our rally car and they're quite secure and handled Rallye Baie des Chaleurs last month without an issue even with some big hits.
This is the bracket, but they're far cheaper from AZE:
https://www.amazon.ca/Amerex-817S-Vehic ... B00F5CKIN2Having said that, we ran a single strap metal bracket that came with our Garrison 2.5LB bottles for 5 years over hundreds of rally kilometres and there was never an issue.
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2005 Forester XT (Daily/
B2Tuned), 2000 Subaru Impreza 2.5RS P4WD Class Rally Car, 2006 WRX RallyCross Car (
Sponsors: Rally-Tech, Great North Performance, ISI Automotive)
Check out:
Rally East,
The Ledwidge Lookoff Rally