I cut some electric front end parts for the Li'l Hacker, basically squaring up the nose just enough to allow the motor(Turnigy 28-20 1640 kV, no longer available). The motor is backplate mounted, with the shaft going through the firewall. This protects it from ground pounding and prevents prop torque from twisting the rotating can into the stator.
1000 mAh 3S E-flight pack, Castle 25 amp ESC and an 8 gr. cheap, cheap, cheap car radio for control. Plane is stock construction.
All up weight is 290 grams(10.2 oz. vs 7oz. for glow power). The battery, ESC, and timer(or receiver) is all of the extra weight including at least 10 grams of wire and extra plugs. With a 7/5 APCe prop it flies exactly like a Cox Black Widow powered version, except it runs 3 min. instead of 2 and it doesn't turn quite as tight The prop is mounted on a flexible mount, secured with an O ring. That works for this low power. Its about 140 watts of power, which almost exactly matches the power and efficiency calculations for the run time. Hobbyking is still listing a Turnigy 2824-1400kV, only a few grams heavier, which can take 20 amps. That would get more performance with the right prop and bring the run time down to a little over 2min.
350 grams seems way too much weight if the basically stock kit can be built to 290. All that carbon fiber and epoxy may be the problem. It is very easy to get 2-3 times more epoxy on it than you need and add an ounce or more. The carbon should be back along the trailing edge and across the center section. There is only needs to go out to about 1/3 span and you can add a 1in strip straight across to form a triangle.
With the motor mounted in a lite ply box there is plenty of room behind that for a hard balsa block to mount a 1/4 in arrowshaft boom. Use hard balsa spars, saves 20 grams over the stock bass spars. Use 1/16 in balsa for a tip rib and 1/16 in sheet for a wing tip of about 2in. span. That brings the wing span and wing area up closer to the Fora sized planes and the longer span will carry the weight better.
BTW, a Fora-powered Yuvenko 1/2A weighs about 225gr. , plus 60 grams of fuel(10 oz.) But it produces about twice the power for twice the time. The best batteries are still twice as heavy as we need!