SqlServer Activerecord Adaptor + VARCHAR(MAX) Woes

I seem to be running into various issues between SqlServer and Rails,
and so far have been able to solve everything save for a particular
quirk when running unit tests.

When I run "rake test:units" on my app, it gets so far as to run
db:schema:load. I'm dealing with a legacy database, so it's loading all
sorts of tables that I don't care about, but regardless, one table in
particular has a column set to VARCHAR(MAX). db:schema:dump interprets
"MAX" as a limit of -1.

Is there a way to set the limit information during the schema dump? I'd
be happy with just setting it to 8000 instead of MAX for testing

I suppose at the very least, I'd like to specify the schema.rb file
myself without rake running db:schema:dump and overwriting my changes.