The man page does not mention that the default value of "mssfix" is 1450.
--- openvpn-2.1.1/openvpn.8 2010-02-28 22:17:45.000000000 +0000 +++ openvpn-2.1.1-a/openvpn.8 2010-04-15 19:43:53.000000000 +0100 @@ -1223,7 +1223,8 @@ their send packet sizes such that after the resulting UDP packet size that OpenVPN sends to its peer will not exceed .B max -bytes. +bytes. The default value is +.B 1450. The .B max -- D.