Yes'sir, Bless EF for coming out with some planes suited for 4# engines. My 56 is in a EF Yak and I really like the way it flies.
I built a 2 into one header to eliminate the extra cannister weight, so there's no weight penalty. Then I found the correct header length, about 13 3/4" from the exhaust flange. It's happiest with a 23x8 Xoar or NX, with NX being a shade better. 6800 rpm on the NX and 6700 on the Xoar. I back the timing off a tad when I found the correct tune length and it helps smooth out transitions and seams to up rpm's a bit. The stock carb runs well but is a larger body than the one on mine now. Also the stock carb has the needles pointing straight up. The smaller body carb on mine now, weighs a couple oz. less, has a slightly larger venturi 34 or 38/64", (I don't remember exactly) and increases rpm's by quite a bit. I can dig up the carb # if needed. Care in placing the engine mount bolts keeps the needles from being right where you don't want them. Do not buy the engine mount that AI sells, the bolt holes will not fit the planes firewall. I can show pics of my mounting bars.