Water Filler Neck Leak

[bikrmikey]

I have a 1971 Caravel. My water tank leaks at the filler neck connection. Presently there is a 1.25" barbed elbow inserted into the tank filler neck and a hose clamp around the filler neck. I replaced the old elbow (it was cracked) and now I have a leak at the connection. No cracks. Tightened the hose clamp as much as possible and got to wondering if this is the proper way to connect to the tank. The rigid tank plastic does not seem to flex with the hose clamp.

My questions are

1. Is the the correct way to connect?

2. Is there a better way?

Thanks

Mike