Foam bodies are stiff & can have a "brush off" effect to rising fish, they are also bulky to tie in unless you use very tight turns which can cut into & weaken them.
By far a better method is to use a length of Flexifloss (NOT spanflex) & tie it in with a twist & furl technique. This is very durable, it moves freely like the natural, it also looks a lot like the natural & is a lot easier to cast as it has no air resistance. To aid bouancy tie it on an u/e sedge hook with a small foam "backpack".
I can't seem to upload pics at the moment, but if you go to
www.photobucket.com then search (people) arkle_photos on page 3 about 7 lines down you'll see a couple of examples there.