Bulk heads on rounded surfaces

[Walter White]

So what are people using for bulkeds on thinks like rubber trash cans, buckets, etc. I found these but dont know how well they work.

http://www.aquacave.com/1-uniseal-flexible-bulkhead-brtank-adapter-1546.html

 

[Wicked Color]

The tension/compression in the threads will flatten out the trash can wall, or what have you.