Informix Version Compatibility Questions

We are currently building our Informix products with Informix version 7.1, linking statically, on a Sun 4 machine, running Solaris 2.4. This makes it possible for the application to connect to a Version 7.1 or 7.2 Server database. However, when our customer installs our product, and they have Informix version 7.2 installed on their machine, our product can't run, because it can't find message files in $INFORMIXDIR/msg. I found that these message files are in $INFORMIXDIR/msg/en_us/0333 in the 7.2 release, and if I just link them to $INFORMIXDIR/msg, it works. Is there a better way to work around this? We considered building with Informix version 7.2, but then when we run our product on a machine that only has Informix version 7.1 installed, we get error -23101: Unableto load locale categories. Is there some way we can work around this problem? I guess my question is, if I have some customers with Informix 7.1, and some with Informix 7.2, am I required to provide two versions of my product, each loaded with the appropriate version of Informix? On a side note, I found that when I linked with either version of Informix, I was still able to connect with a Version 7.2 server database. Is it also possible to connect with a version 7.1 server database if my product is loaded with version 7.2 of Informix? Thanks for any help.