NW5.1 Disk Duplexing

I’ve a NW5.1 Server with disk duplexing installed. I need to change the disks with vol sys to larger ones. My question: Is it possible to replace one of the mirrored/duplexed disks with one of the new larger ones. Then remirror and do so with the remaining old disk. I’ve read in the novell documentation that the new mirror partition has to be the same size than the original one. So I think that my “solution” is not the right way. Are there any other “simple” chances to change the disks? Maybe with third party products.