as far as i know, there is no way to change the partial files. you might try using the search feature and looking for other posts on this subject. It would also be beneficial if you read up on downloads stuck at 99%. This too is in other posts. I just don't feel like looking for them specifically. The seach feature at the top right hand side of the page seems to work well though.
I understand that you want the files that you are downloading, but here is another thought: why would you want incomplete files on your computer. This makes me furious when i download partially completed files from some other types of gnutella p2ps. I know that bearshare used to be like this, because i used to use it as well. Also, please be kind to the many folks like me that do not want you partially completed files and do not share these files(that is if you figure out how to change the format).
Happy Dowloading