Here's my 1.5" setup from Brewer's Hardware. One mistake I made - had the ferrule welded on too low (done before the enclosure arrived because I was like a kid on Christmas Eve and couldn't wait!). Was trying to get the element as low in the kettle as possible since I BIAB 5 gal batches in an 11 gal kettle and wanted as much clearance as possible for my false bottom.
Anyway - the cap on the 1.5" is considerably larger than the diameter of the enclosure itself. Just be aware of that and place the ferrule appropriately. My fault for jumping the gun, but I've accounted for it in the design for my new stand.