This StarLink adapter will mount Dishy (rectangular) onto a tripod. The bottom hole will fit a 1 inch post (like the one on this tripod) and inside the base there's a hole for for a standard large tripod bolt and a recess to hold onto a 3/8-16 nut. This should provide a very strong positive clamping force and support the lateral forces on the dish and tripod.

It's designed to be printed without overhangs, in two pieces. I recommend ASA or ABS to survive outdoors, because PLA will soften in the sun and degrade in UV pretty quickly. The two halves are attached with M3x12 screws and M3 heat-sets. If you're printing with a 0.4 nozzle you should do at least 4 shells and 50% infill. Larger nozzles require fewer shells.

You could also use strong CA glue to hold the two halves together, with a zip-tie around it all just to make sure it doesn't separate.

If you'd like to work off my CAD file you can find it in OnShape here: https://cad.onshape.com/documents/06ce2764eb8b50d1b2ed4f62/w/06bed2e327c5df4a48a5c7d5/e/b73888040156b4e42777c81d?explodedView=MPgeTWlZRhsawTvVm&renderMode=4&tangentEdgeStyle=1&rightPanel=explodedViewPanel&uiState=655447feeada595258e06023