There are a few off the shelf rods with a mix. There is one on the market just now, and I cant for the life of remember what make it is...possibly Hanak, as its a euro nymph set up. The very tip has singles, the rest doubles.
There are a few things to remember when configuring the guides....weight and stiffness.
You can "tweak" the action of the rod not only by the placement of guides, but also whether you use double or single legged and the weight of extra epoxy and thread.
I have a deflection board at home that I use to static place guides. I can change the curve of the blank, making it "flatter" by using double legged, or giving it a more natural curve using singles. I can also slightly shift the curve to being a little more tippy
Doubles act as a brace because with the 2 feet being apart, plus the epoxy on the whipping, you are effectively inserting stiffners up the blank.
So, the effect of having doubles on 3/4 of the blank and singles on the top 1/4 will be to shift the bias to a slightly softer tip.
There will also be a little less "bounce" at the end of a cast as there is a little less weight.