I've tried width mates to constrain the strap to stay inside the buckle. I got it mostly constrained, but the buckle can still move below the strap as shown. Also I am aware that the strap and/or buckle is the wrong size. I'm going to fix that.
I use sketches on parts that have complex geometry. On this assembly I created a plane referencing the dome and the face opposite, then I sketched( converted entities) a circle . The sketch is what I use for the mate on this sub-assembly.
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