Ultegra 6500 exage 500 cantilever question

[heavymetal]

Hi
I'm considering building a tourer with old but serviceable components but with a new cheap frame
I have a group set compatibility question which somebody may be able to answer
Are Ultegra 6500 sti levers (brake lever part) compatible with the old Exage 500 cantilever brakes?
Is it an efficient combination or will it be spongy and weak
I'm sure I have seen this combination on some touring bikes in the past.

http://velobase.com/ViewComponent.aspx? ... 5&Enum=117