Larry,
I was thinking of doing this myself. It's a project that is in line behind many other projects. I have Bat-Racks that mount to the flat side of a 3" oval tube. Was thinking of using some Architectural Aluminum Channel 3" x 1".
and put them together... sorta like this
The problem is, the only channel I can find in 1x3 is 1/8" thick. I'm concerned that 1/8 will be too thin.
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Then was thinking of:
But it probably won't be strong enough.. especially with wind.
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So was thinking of something like this, with an incline plane so it would auto latch:
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And some Lanyards to limit range.
Or maybe some gas-struts
If you endup building something, keep me posted. I'd like to see what you come up with.