I can't see any risk, but i think the better way to do this was creating long text through SO10 transaction. And populating this long text in your z program....
Remember with the string field has a lenght of 255 characteres.... Thats the only problem i can see...
To change this, will be necessary create a routine to migrate the data from string field to long text, or do this manually.
If you need more help about use long text let me know...
Regards