Data read errors during parity rebuild - way ahead?

I am in the process of rebuilding parity on a larger disk.  Due to other errors reported in an earlier thread, I am rebuilding on a single parity disk instead of the two I had previously.  I am about 6% through the rebuild and just got informed of read errors on one of my older data disks. 

Since I still have the older parity disks, I believe I can recover from this. What I plan to do is this:

1. Let the rebuild complete and hope for no other errors, or at least no other disks with errors.
2. After the rebuild completes, stop the array, power down.  Replace the newly built parity drive with the two old ones. Remove the data drive with the read errors and replace it with a new (precleared) drive (which will have to be larger than the original).
3. Restart the array, let it rebuild the data disk.  After the rebuild, stop and shut down again.
4. Pull out the two old parity drives, replace with the one which was just rebuilt.  It's now invalid, so rebuild it yet again.

I am letting the current rebuild complete, at least for now, because I'm not entirely sure the steps above will work, and that I may not want that as a valid disk except the the sectors with read errors.  I'm also worried that as the parity rebuild started all the data disks got a small number of writes - I wasn't expecting that and it worries me.  But that rebuild has over a day to go before it completes.

I'd appreciate your advice as to whether the steps above should work, whether I should let the current rebuild complete, and anything else I should know about this situation.  Also how to "force rebuild" a parity disk - I suppose in my case that's just a parity check by any other name.

Thanks!