Subject Issues with blobs in FB 2.5?

We've developed, and are distributing an application (Windows, C++) that
uses Firebird for its data management. We are currently in the process of
upgrading from FB 2.0 to FB 2.5.

I'm wondering precisely what validity checks are being performed on
character blobs in 2.5, i.e., the ones that may lead to a "malformed string"

In our tables there are blob columns defined to be of sub-type 1, even though
the data are not necessarily character data at all. Over the years - including
the past few months, when I've been using 2.5 in my development
environment - we've experienced no problems, other than a couple where no
charset had been specified for the blob. (Our default charset is UTF8.)

I'm wondering whether recent changes, or expected changes, might result in
problems when inserting to columns currently defined as "blob sub_type 1
segment size 400 CHARACTER SET ASCII". (The app accesses Firebird
through the ODBC interface, with "outgoing" data parameters bound with a
ValueType or SQL_C_CHAR and a ParameterType of

Thanks for any info,