Rafa,

I think it is generally hard to build super light airframes using classic construction methods - especially in the scaled down versions. The smaller the model, the more careful one has to be. Using foam cores should help if built light although doing a built up flat stab is also a good option at the scale you're building. Still, its possible that an airfoiled foam core stab might weigh less than a built up flat one at considerably higher strength.

My D10 will likely be in the 40 oz range AUW, heavy by today's standards for a 40" model. However, the Deception is a wide wing model and the D10 has over 300 sq in of area which brings the model in with an acceptable wing loading. The same is not true of the 40" Pico which has wing area in the mid to upper 200 sq in (I haven't figured it out the area yet). I'm not sure what your figure of 19.5 oz constitutes but my gut feeling is that Pico's with retracts should come in around the 36 oz (2.25 lbs) mark - 34 would be better. Of course omitting landing gear takes care of a few weight problems - hand launch, grass land. Again, my instinct on an electric Pico would be to omit LG, keep the servo count to 4 (I think 3 servos would end up weighing the same with today's crop of 0.3-0.4 oz servos which weigh the same or less than torque rods), and mount the motor in a simple fashion using carbon rod spacers if necessary. In the absence of retracts, it would be pretty simple to just move the FW forward to where its needed and mount the outrunner directly to it with an X mount. This also provides more room to locate your power gear (battery, ESC, etc.). You also wouldn't need a BEC with 4 micro servos.

Regarding the TP, thanks for that clarification. I suspected that this is what rendered it nose heavy. One option would be to tail mount the servos when planning to use a TP to offset the nose weight (4 cycle style). With an electric, you'd have a lot of room to fit two servos, a micro Rx, an ESC and the battery. Avoid the wing fillets, possibly use 1/16" fuse sides laminated with 1/32" ply full length and drill out the sides at will to lighten. Likewise on the fuse top, bottom and solid control surfaces (elevator and ailerons). I think if built like that, you could easily bring in a Pico airframe in the sub one pound weight ballpark for an AUW of ~36 oz (if your gear is weighing ~20 oz)

Just a few thoughts, David.