voltmeter motorcycle mount

I bought a voltmeter off Amazon with a 3 cm bore specification. I wanted a small mount to go between my speedo and tach so i can diagnose my charging system on the road, so I whipped one up. Cable port is wide enough for the connector to pass through for easier wiring. Mounts with one M3 screw from the back, and if you have one long enough, it'll screw into a nut, which i put a recess in for. If not, as long as you only screw it in once, it seems like you can get it tight enough to hold just in the plastic.

Link to voltmeter: https://www.amazon.ca/dp/B0BN1J77C4?psc=1&ref=ppx_yo2ov_dt_b_product_details