Solr 4.2 update/extract adding unknown field, can we change field type from string to text

[Jai]

hi,

while indexing document with unknown fields, its adding unknown fields in
schema but its always guessing it as string type. is it possible to specify
default field type for unknown fields to some other type, like text so that
it gets tokenized? also can we specify other properties by default like
indexed/stored/multivalued?

PS am using solr4.2.

Thanks alot.
Jai