Have you looked at All About Spelling? It's taken from SWR. I've used SWR with all 5 of my children. Actually, with the older ones, I used Romalda Spaulding's Writing Road to Reading which was waaay too complicated. SWR came from this and was made simpler. Anyway, I've found the same problems with my 11yo son that you've described in your post. I think that all of my children made many of the same careless errors at this age. The older ones outgrew it, and hopefully he will to. Back to All About Spelling, (sorry ;-).....there are manipulatives, ie. phonogram tiles, to use on a magnetic board. It sounded really young for me to use with him, but it is helping. Check out the site
http://www.allaboutspelling.com
They will explain it much better than I can as I am short on time. Hope this helps.....Mindy