Problems accessing sites hosted by 1and1 (probably an MTU issue)

[WilliamMPLX]

Whenever I try and access a site hosted by 1and1 over the tunnel (e.g. http://www.icydock.com/ ) I get an "ERR_CONNECTION_RESET" message from Chrome.

My local tunnel endpoint is a Ubiquiti EdgeMAX.


Having done some testing, I've found that:

IPv6 sites hosted elsewhere seem fine.
The same sites can be accessed fine over a native IPv6 connection.
I have the MTU set at both ends to 1472 -any higher and every site I try breaks (I think 1472 is the correct value anyway, on the basis of the IPv4 under the tunnel having an MTU of 1492).
I've also tried setting the MTU down to 1280 just to see if that helped.

Having done that, I'm not really sure where to go next to troubleshoot this?

Any help would be gratefully received!