Tall flag for visibility on trailer

I just brought home my PA 17T with the Hobie trailer designed for it. The boat on the trailer sits very low and I was concerned about visibility of the trailer to other drivers (Many crazy drivers around here. They change lanes with nothing more than a cursory glance). On my initial trip home I left a visibility flag in one of the rear rod holders (a flag I purchased for use on the water). Unfortunately the flag was not up to the challenge of the constant 65 mph winds of highway travel. The thin fiberglass pole cracked under the strain and the flag part flew off. Guess I'll be buying a new flag for the water. But I still like the idea of a tall flag for trailering; I just need one that can handle the strain. Maybe mounted to the trailer itself. My initial google searches showed only flags for bicycle trailers which I think would suffer the same fate as my kayak flag. Any here have suggestions?
Thanks!

I installed two fiberglass rods and the top end has 2" wide, red reflective tape for both "on the road visibility at night" plus I can see the trailer when backing it up.
In addition, my trailers brake/tail lights are "U-bolt mounted" to the aft carrying handle on my PA-14 for traffic behind, to better see the trailer lights.

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Dr.SteelheadCatcher
Warrenton, OR

California law: "Whenever the load upon any vehicle extends, or whenever any integral part of any vehicle projects, to the rear 4 feet or more beyond the rear of the vehicle, as measured from the tail lamps, there shall be displayed at the extreme end of the load or projecting part of the vehicle during darkness, in addition to the required tail lamp, two red lights with a bulb rated not in excess of six candlepower plainly visible from a distance of at least 500 feet to the sides and rear. At any other time there shall be displayed at the extreme end of the load or projecting part of the vehicle a solid red or fluorescent orange flag or cloth not less than 12 inches square."

I interpret this as attached at the end of the load. However, I don’t think that this would preclude from you using a flag on a rod also.

I have a 17t on a trailer too, and I don't have a flag. It really hasn't been a concern of mine because I think you have to be absolutely blind not to see a 17 ft kayak on a trailer. If you want to be cautious, consider getting an H-Bar. I leave it up all the time and it looks pretty cool. Plus, it is useful when on the water.

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Vegasvec
2015 Pro Angler 17t
Lowrance Elite 5 Chirp
Zieman Trailer w/ Cradles