Here's a site with some good Carp flies. My personal favorite is the Lil Bugger, especially in Brown/Tan. Barry's Carp fly has also been very productive. I've read a few posts and the Clouser Swimming Nymph seems to be a winner.
I rarely throw anything bigger than #8's for Carp. I use floro tippet and usually go with 3X. My biggest Carp, 31", came on a #8 olive craw using my 5wt. I have also caught several 4-5 lbers on my 3wt. I was fishing for SM and Rockies with the 3wt when I saw a pod of Carp and couldn't pass it up. I pulled 4 fish out of the group and landed 3 of them.
MTD - The only comment I have about your technique is to downsize a little. But if it works, don't change.