For anyone looking to attach dishy to a j-mount, this would be a good way to attach it without having to buy starlink's adaptor: Pro Signal Antenna Mast Clamp Clamp Two Masts Up to 2" - 33-12256 https://smile.amazon.com/dp/B07NVJ1C67/ref=cm_sw_r_apan_glt_fabc_JA8YMRNVERTRN8ACTDYQ?_encoding=UTF8&psc=1
Here's a link for a u-bolt made for two masts. I've seen other similar products but my coffee is getting cold.