Sony ZV-E10 custom tripod stability test vlog in Brighton

I've been trying to find a way to get stable video shots with my Sony ZV-E10 and Tamron 18-300mm lens without carrying around tripods, gimbals, or monopods.
In today's video, I took a break from working to ride the Volks Railway - the world's oldest operating electric railway - into Brighton to get some donuts on the pier and test out a small mini tripod concept I've put together that works even with such a long lens at full extension.
I'm pretty happy with the stability, but I'm not sure it's quite there yet. If you have any other ideas, please leave them in the comments.